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<h1>Node.js v20.18.0 documentation</h1>
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Table of contents
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<li><span class="stability_2"><a href="#net">Net</a></span>
<ul>
<li><a href="#ipc-support">IPC support</a>
<ul>
<li><a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a></li>
</ul>
</li>
<li><a href="#class-netblocklist">Class: <code>net.BlockList</code></a>
<ul>
<li><a href="#blocklistaddaddressaddress-type"><code>blockList.addAddress(address[, type])</code></a></li>
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<ul>
<li><a href="#new-netsocketaddressoptions"><code>new net.SocketAddress([options])</code></a></li>
<li><a href="#socketaddressaddress"><code>socketaddress.address</code></a></li>
<li><a href="#socketaddressfamily"><code>socketaddress.family</code></a></li>
<li><a href="#socketaddressflowlabel"><code>socketaddress.flowlabel</code></a></li>
<li><a href="#socketaddressport"><code>socketaddress.port</code></a></li>
</ul>
</li>
<li><a href="#class-netserver">Class: <code>net.Server</code></a>
<ul>
<li><a href="#new-netserveroptions-connectionlistener"><code>new net.Server([options][, connectionListener])</code></a></li>
<li><a href="#event-close">Event: <code>'close'</code></a></li>
<li><a href="#event-connection">Event: <code>'connection'</code></a></li>
<li><a href="#event-error">Event: <code>'error'</code></a></li>
<li><a href="#event-listening">Event: <code>'listening'</code></a></li>
<li><a href="#event-drop">Event: <code>'drop'</code></a></li>
<li><a href="#serveraddress"><code>server.address()</code></a></li>
<li><a href="#serverclosecallback"><code>server.close([callback])</code></a></li>
<li><span class="stability_1"><a href="#serversymbolasyncdispose"><code>server[Symbol.asyncDispose]()</code></a></span></li>
<li><a href="#servergetconnectionscallback"><code>server.getConnections(callback)</code></a></li>
<li><a href="#serverlisten"><code>server.listen()</code></a>
<ul>
<li><a href="#serverlistenhandle-backlog-callback"><code>server.listen(handle[, backlog][, callback])</code></a></li>
<li><a href="#serverlistenoptions-callback"><code>server.listen(options[, callback])</code></a></li>
<li><a href="#serverlistenpath-backlog-callback"><code>server.listen(path[, backlog][, callback])</code></a></li>
<li><a href="#serverlistenport-host-backlog-callback"><code>server.listen([port[, host[, backlog]]][, callback])</code></a></li>
</ul>
</li>
<li><a href="#serverlistening"><code>server.listening</code></a></li>
<li><a href="#servermaxconnections"><code>server.maxConnections</code></a></li>
<li><a href="#serverref"><code>server.ref()</code></a></li>
<li><a href="#serverunref"><code>server.unref()</code></a></li>
</ul>
</li>
<li><a href="#class-netsocket">Class: <code>net.Socket</code></a>
<ul>
<li><a href="#new-netsocketoptions"><code>new net.Socket([options])</code></a></li>
<li><a href="#event-close_1">Event: <code>'close'</code></a></li>
<li><a href="#event-connect">Event: <code>'connect'</code></a></li>
<li><a href="#event-connectionattempt">Event: <code>'connectionAttempt'</code></a></li>
<li><a href="#event-connectionattemptfailed">Event: <code>'connectionAttemptFailed'</code></a></li>
<li><a href="#event-connectionattempttimeout">Event: <code>'connectionAttemptTimeout'</code></a></li>
<li><a href="#event-data">Event: <code>'data'</code></a></li>
<li><a href="#event-drain">Event: <code>'drain'</code></a></li>
<li><a href="#event-end">Event: <code>'end'</code></a></li>
<li><a href="#event-error_1">Event: <code>'error'</code></a></li>
<li><a href="#event-lookup">Event: <code>'lookup'</code></a></li>
<li><a href="#event-ready">Event: <code>'ready'</code></a></li>
<li><a href="#event-timeout">Event: <code>'timeout'</code></a></li>
<li><a href="#socketaddress"><code>socket.address()</code></a></li>
<li><a href="#socketautoselectfamilyattemptedaddresses"><code>socket.autoSelectFamilyAttemptedAddresses</code></a></li>
<li><span class="stability_0"><a href="#socketbuffersize"><code>socket.bufferSize</code></a></span></li>
<li><a href="#socketbytesread"><code>socket.bytesRead</code></a></li>
<li><a href="#socketbyteswritten"><code>socket.bytesWritten</code></a></li>
<li><a href="#socketconnect"><code>socket.connect()</code></a>
<ul>
<li><a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a></li>
<li><a href="#socketconnectpath-connectlistener"><code>socket.connect(path[, connectListener])</code></a></li>
<li><a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a></li>
</ul>
</li>
<li><a href="#socketconnecting"><code>socket.connecting</code></a></li>
<li><a href="#socketdestroyerror"><code>socket.destroy([error])</code></a></li>
<li><a href="#socketdestroyed"><code>socket.destroyed</code></a></li>
<li><a href="#socketdestroysoon"><code>socket.destroySoon()</code></a></li>
<li><a href="#socketenddata-encoding-callback"><code>socket.end([data[, encoding]][, callback])</code></a></li>
<li><a href="#socketlocaladdress"><code>socket.localAddress</code></a></li>
<li><a href="#socketlocalport"><code>socket.localPort</code></a></li>
<li><a href="#socketlocalfamily"><code>socket.localFamily</code></a></li>
<li><a href="#socketpause"><code>socket.pause()</code></a></li>
<li><a href="#socketpending"><code>socket.pending</code></a></li>
<li><a href="#socketref"><code>socket.ref()</code></a></li>
<li><a href="#socketremoteaddress"><code>socket.remoteAddress</code></a></li>
<li><a href="#socketremotefamily"><code>socket.remoteFamily</code></a></li>
<li><a href="#socketremoteport"><code>socket.remotePort</code></a></li>
<li><a href="#socketresetanddestroy"><code>socket.resetAndDestroy()</code></a></li>
<li><a href="#socketresume"><code>socket.resume()</code></a></li>
<li><a href="#socketsetencodingencoding"><code>socket.setEncoding([encoding])</code></a></li>
<li><a href="#socketsetkeepaliveenable-initialdelay"><code>socket.setKeepAlive([enable][, initialDelay])</code></a></li>
<li><a href="#socketsetnodelaynodelay"><code>socket.setNoDelay([noDelay])</code></a></li>
<li><a href="#socketsettimeouttimeout-callback"><code>socket.setTimeout(timeout[, callback])</code></a></li>
<li><a href="#sockettimeout"><code>socket.timeout</code></a></li>
<li><a href="#socketunref"><code>socket.unref()</code></a></li>
<li><a href="#socketwritedata-encoding-callback"><code>socket.write(data[, encoding][, callback])</code></a></li>
<li><a href="#socketreadystate"><code>socket.readyState</code></a></li>
</ul>
</li>
<li><a href="#netconnect"><code>net.connect()</code></a>
<ul>
<li><a href="#netconnectoptions-connectlistener"><code>net.connect(options[, connectListener])</code></a></li>
<li><a href="#netconnectpath-connectlistener"><code>net.connect(path[, connectListener])</code></a></li>
<li><a href="#netconnectport-host-connectlistener"><code>net.connect(port[, host][, connectListener])</code></a></li>
</ul>
</li>
<li><a href="#netcreateconnection"><code>net.createConnection()</code></a>
<ul>
<li><a href="#netcreateconnectionoptions-connectlistener"><code>net.createConnection(options[, connectListener])</code></a></li>
<li><a href="#netcreateconnectionpath-connectlistener"><code>net.createConnection(path[, connectListener])</code></a></li>
<li><a href="#netcreateconnectionport-host-connectlistener"><code>net.createConnection(port[, host][, connectListener])</code></a></li>
</ul>
</li>
<li><a href="#netcreateserveroptions-connectionlistener"><code>net.createServer([options][, connectionListener])</code></a></li>
<li><a href="#netgetdefaultautoselectfamily"><code>net.getDefaultAutoSelectFamily()</code></a></li>
<li><a href="#netsetdefaultautoselectfamilyvalue"><code>net.setDefaultAutoSelectFamily(value)</code></a></li>
<li><a href="#netgetdefaultautoselectfamilyattempttimeout"><code>net.getDefaultAutoSelectFamilyAttemptTimeout()</code></a></li>
<li><a href="#netsetdefaultautoselectfamilyattempttimeoutvalue"><code>net.setDefaultAutoSelectFamilyAttemptTimeout(value)</code></a></li>
<li><a href="#netisipinput"><code>net.isIP(input)</code></a></li>
<li><a href="#netisipv4input"><code>net.isIPv4(input)</code></a></li>
<li><a href="#netisipv6input"><code>net.isIPv6(input)</code></a></li>
</ul>
</li>
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<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li>
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Other versions
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<div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v22.x/api/net.html">22.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v21.x/api/net.html">21.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v20.x/api/net.html">20.x <b>LTS</b></a></li>
<li><a href="https://nodejs.org/docs/latest-v19.x/api/net.html">19.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v18.x/api/net.html">18.x <b>LTS</b></a></li>
<li><a href="https://nodejs.org/docs/latest-v17.x/api/net.html">17.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v16.x/api/net.html">16.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v15.x/api/net.html">15.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v14.x/api/net.html">14.x</a></li>
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<li><a href="https://nodejs.org/docs/latest-v11.x/api/net.html">11.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v10.x/api/net.html">10.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v9.x/api/net.html">9.x</a></li>
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<li><a href="https://nodejs.org/docs/latest-v6.x/api/net.html">6.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v5.x/api/net.html">5.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v4.x/api/net.html">4.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/net.html">0.12.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/net.html">0.10.x</a></li></ol></div>
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<hr>
</header>
<details role="navigation" id="toc" open><summary>Table of contents</summary><ul>
<li><span class="stability_2"><a href="#net">Net</a></span>
<ul>
<li><a href="#ipc-support">IPC support</a>
<ul>
<li><a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a></li>
</ul>
</li>
<li><a href="#class-netblocklist">Class: <code>net.BlockList</code></a>
<ul>
<li><a href="#blocklistaddaddressaddress-type"><code>blockList.addAddress(address[, type])</code></a></li>
<li><a href="#blocklistaddrangestart-end-type"><code>blockList.addRange(start, end[, type])</code></a></li>
<li><a href="#blocklistaddsubnetnet-prefix-type"><code>blockList.addSubnet(net, prefix[, type])</code></a></li>
<li><a href="#blocklistcheckaddress-type"><code>blockList.check(address[, type])</code></a></li>
<li><a href="#blocklistrules"><code>blockList.rules</code></a></li>
</ul>
</li>
<li><a href="#class-netsocketaddress">Class: <code>net.SocketAddress</code></a>
<ul>
<li><a href="#new-netsocketaddressoptions"><code>new net.SocketAddress([options])</code></a></li>
<li><a href="#socketaddressaddress"><code>socketaddress.address</code></a></li>
<li><a href="#socketaddressfamily"><code>socketaddress.family</code></a></li>
<li><a href="#socketaddressflowlabel"><code>socketaddress.flowlabel</code></a></li>
<li><a href="#socketaddressport"><code>socketaddress.port</code></a></li>
</ul>
</li>
<li><a href="#class-netserver">Class: <code>net.Server</code></a>
<ul>
<li><a href="#new-netserveroptions-connectionlistener"><code>new net.Server([options][, connectionListener])</code></a></li>
<li><a href="#event-close">Event: <code>'close'</code></a></li>
<li><a href="#event-connection">Event: <code>'connection'</code></a></li>
<li><a href="#event-error">Event: <code>'error'</code></a></li>
<li><a href="#event-listening">Event: <code>'listening'</code></a></li>
<li><a href="#event-drop">Event: <code>'drop'</code></a></li>
<li><a href="#serveraddress"><code>server.address()</code></a></li>
<li><a href="#serverclosecallback"><code>server.close([callback])</code></a></li>
<li><span class="stability_1"><a href="#serversymbolasyncdispose"><code>server[Symbol.asyncDispose]()</code></a></span></li>
<li><a href="#servergetconnectionscallback"><code>server.getConnections(callback)</code></a></li>
<li><a href="#serverlisten"><code>server.listen()</code></a>
<ul>
<li><a href="#serverlistenhandle-backlog-callback"><code>server.listen(handle[, backlog][, callback])</code></a></li>
<li><a href="#serverlistenoptions-callback"><code>server.listen(options[, callback])</code></a></li>
<li><a href="#serverlistenpath-backlog-callback"><code>server.listen(path[, backlog][, callback])</code></a></li>
<li><a href="#serverlistenport-host-backlog-callback"><code>server.listen([port[, host[, backlog]]][, callback])</code></a></li>
</ul>
</li>
<li><a href="#serverlistening"><code>server.listening</code></a></li>
<li><a href="#servermaxconnections"><code>server.maxConnections</code></a></li>
<li><a href="#serverref"><code>server.ref()</code></a></li>
<li><a href="#serverunref"><code>server.unref()</code></a></li>
</ul>
</li>
<li><a href="#class-netsocket">Class: <code>net.Socket</code></a>
<ul>
<li><a href="#new-netsocketoptions"><code>new net.Socket([options])</code></a></li>
<li><a href="#event-close_1">Event: <code>'close'</code></a></li>
<li><a href="#event-connect">Event: <code>'connect'</code></a></li>
<li><a href="#event-connectionattempt">Event: <code>'connectionAttempt'</code></a></li>
<li><a href="#event-connectionattemptfailed">Event: <code>'connectionAttemptFailed'</code></a></li>
<li><a href="#event-connectionattempttimeout">Event: <code>'connectionAttemptTimeout'</code></a></li>
<li><a href="#event-data">Event: <code>'data'</code></a></li>
<li><a href="#event-drain">Event: <code>'drain'</code></a></li>
<li><a href="#event-end">Event: <code>'end'</code></a></li>
<li><a href="#event-error_1">Event: <code>'error'</code></a></li>
<li><a href="#event-lookup">Event: <code>'lookup'</code></a></li>
<li><a href="#event-ready">Event: <code>'ready'</code></a></li>
<li><a href="#event-timeout">Event: <code>'timeout'</code></a></li>
<li><a href="#socketaddress"><code>socket.address()</code></a></li>
<li><a href="#socketautoselectfamilyattemptedaddresses"><code>socket.autoSelectFamilyAttemptedAddresses</code></a></li>
<li><span class="stability_0"><a href="#socketbuffersize"><code>socket.bufferSize</code></a></span></li>
<li><a href="#socketbytesread"><code>socket.bytesRead</code></a></li>
<li><a href="#socketbyteswritten"><code>socket.bytesWritten</code></a></li>
<li><a href="#socketconnect"><code>socket.connect()</code></a>
<ul>
<li><a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a></li>
<li><a href="#socketconnectpath-connectlistener"><code>socket.connect(path[, connectListener])</code></a></li>
<li><a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a></li>
</ul>
</li>
<li><a href="#socketconnecting"><code>socket.connecting</code></a></li>
<li><a href="#socketdestroyerror"><code>socket.destroy([error])</code></a></li>
<li><a href="#socketdestroyed"><code>socket.destroyed</code></a></li>
<li><a href="#socketdestroysoon"><code>socket.destroySoon()</code></a></li>
<li><a href="#socketenddata-encoding-callback"><code>socket.end([data[, encoding]][, callback])</code></a></li>
<li><a href="#socketlocaladdress"><code>socket.localAddress</code></a></li>
<li><a href="#socketlocalport"><code>socket.localPort</code></a></li>
<li><a href="#socketlocalfamily"><code>socket.localFamily</code></a></li>
<li><a href="#socketpause"><code>socket.pause()</code></a></li>
<li><a href="#socketpending"><code>socket.pending</code></a></li>
<li><a href="#socketref"><code>socket.ref()</code></a></li>
<li><a href="#socketremoteaddress"><code>socket.remoteAddress</code></a></li>
<li><a href="#socketremotefamily"><code>socket.remoteFamily</code></a></li>
<li><a href="#socketremoteport"><code>socket.remotePort</code></a></li>
<li><a href="#socketresetanddestroy"><code>socket.resetAndDestroy()</code></a></li>
<li><a href="#socketresume"><code>socket.resume()</code></a></li>
<li><a href="#socketsetencodingencoding"><code>socket.setEncoding([encoding])</code></a></li>
<li><a href="#socketsetkeepaliveenable-initialdelay"><code>socket.setKeepAlive([enable][, initialDelay])</code></a></li>
<li><a href="#socketsetnodelaynodelay"><code>socket.setNoDelay([noDelay])</code></a></li>
<li><a href="#socketsettimeouttimeout-callback"><code>socket.setTimeout(timeout[, callback])</code></a></li>
<li><a href="#sockettimeout"><code>socket.timeout</code></a></li>
<li><a href="#socketunref"><code>socket.unref()</code></a></li>
<li><a href="#socketwritedata-encoding-callback"><code>socket.write(data[, encoding][, callback])</code></a></li>
<li><a href="#socketreadystate"><code>socket.readyState</code></a></li>
</ul>
</li>
<li><a href="#netconnect"><code>net.connect()</code></a>
<ul>
<li><a href="#netconnectoptions-connectlistener"><code>net.connect(options[, connectListener])</code></a></li>
<li><a href="#netconnectpath-connectlistener"><code>net.connect(path[, connectListener])</code></a></li>
<li><a href="#netconnectport-host-connectlistener"><code>net.connect(port[, host][, connectListener])</code></a></li>
</ul>
</li>
<li><a href="#netcreateconnection"><code>net.createConnection()</code></a>
<ul>
<li><a href="#netcreateconnectionoptions-connectlistener"><code>net.createConnection(options[, connectListener])</code></a></li>
<li><a href="#netcreateconnectionpath-connectlistener"><code>net.createConnection(path[, connectListener])</code></a></li>
<li><a href="#netcreateconnectionport-host-connectlistener"><code>net.createConnection(port[, host][, connectListener])</code></a></li>
</ul>
</li>
<li><a href="#netcreateserveroptions-connectionlistener"><code>net.createServer([options][, connectionListener])</code></a></li>
<li><a href="#netgetdefaultautoselectfamily"><code>net.getDefaultAutoSelectFamily()</code></a></li>
<li><a href="#netsetdefaultautoselectfamilyvalue"><code>net.setDefaultAutoSelectFamily(value)</code></a></li>
<li><a href="#netgetdefaultautoselectfamilyattempttimeout"><code>net.getDefaultAutoSelectFamilyAttemptTimeout()</code></a></li>
<li><a href="#netsetdefaultautoselectfamilyattempttimeoutvalue"><code>net.setDefaultAutoSelectFamilyAttemptTimeout(value)</code></a></li>
<li><a href="#netisipinput"><code>net.isIP(input)</code></a></li>
<li><a href="#netisipv4input"><code>net.isIPv4(input)</code></a></li>
<li><a href="#netisipv6input"><code>net.isIPv6(input)</code></a></li>
</ul>
</li>
</ul></details>
<div role="main" id="apicontent">
<h2>Net<span><a class="mark" href="#net" id="net">#</a></span><a aria-hidden="true" class="legacy" id="net_net"></a></h2>
<!--lint disable maximum-line-length-->
<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p>
<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v20.18.0/lib/net.js">lib/net.js</a></p>
<p>The <code>node:net</code> module provides an asynchronous network API for creating stream-based
TCP or <a href="#ipc-support">IPC</a> servers (<a href="#netcreateserveroptions-connectionlistener"><code>net.createServer()</code></a>) and clients
(<a href="#netcreateconnection"><code>net.createConnection()</code></a>).</p>
<p>It can be accessed using:</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> net = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>);</code> <button class="copy-button">copy</button></pre>
<section><h3>IPC support<span><a class="mark" href="#ipc-support" id="ipc-support">#</a></span><a aria-hidden="true" class="legacy" id="net_ipc_support"></a></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v20.8.0</td>
<td><p>Support binding to abstract Unix domain socket path like <code>\0abstract</code>. We can bind '\0' for Node.js <code>< v20.4.0</code>.</p></td></tr>
</tbody></table>
</details>
</div>
<p>The <code>node:net</code> module supports IPC with named pipes on Windows, and Unix domain
sockets on other operating systems.</p>
<h4>Identifying paths for IPC connections<span><a class="mark" href="#identifying-paths-for-ipc-connections" id="identifying-paths-for-ipc-connections">#</a></span><a aria-hidden="true" class="legacy" id="net_identifying_paths_for_ipc_connections"></a></h4>
<p><a href="#netconnect"><code>net.connect()</code></a>, <a href="#netcreateconnection"><code>net.createConnection()</code></a>, <a href="#serverlisten"><code>server.listen()</code></a>, and
<a href="#socketconnect"><code>socket.connect()</code></a> take a <code>path</code> parameter to identify IPC endpoints.</p>
<p>On Unix, the local domain is also known as the Unix domain. The path is a
file system pathname. It gets truncated to an OS-dependent length of
<code>sizeof(sockaddr_un.sun_path) - 1</code>. Typical values are 107 bytes on Linux and
103 bytes on macOS. If a Node.js API abstraction creates the Unix domain socket,
it will unlink the Unix domain socket as well. For example,
<a href="#netcreateserveroptions-connectionlistener"><code>net.createServer()</code></a> may create a Unix domain socket and
<a href="#serverclosecallback"><code>server.close()</code></a> will unlink it. But if a user creates the Unix domain
socket outside of these abstractions, the user will need to remove it. The same
applies when a Node.js API creates a Unix domain socket but the program then
crashes. In short, a Unix domain socket will be visible in the file system and
will persist until unlinked. On Linux, You can use Unix abstract socket by adding
<code>\0</code> to the beginning of the path, such as <code>\0abstract</code>. The path to the Unix
abstract socket is not visible in the file system and it will disappear automatically
when all open references to the socket are closed.</p>
<p>On Windows, the local domain is implemented using a named pipe. The path <em>must</em>
refer to an entry in <code>\\?\pipe\</code> or <code>\\.\pipe\</code>. Any characters are permitted,
but the latter may do some processing of pipe names, such as resolving <code>..</code>
sequences. Despite how it might look, the pipe namespace is flat. Pipes will
<em>not persist</em>. They are removed when the last reference to them is closed.
Unlike Unix domain sockets, Windows will close and remove the pipe when the
owning process exits.</p>
<p>JavaScript string escaping requires paths to be specified with extra backslash
escaping such as:</p>
<pre><code class="language-js">net.<span class="hljs-title function_">createServer</span>().<span class="hljs-title function_">listen</span>(
path.<span class="hljs-title function_">join</span>(<span class="hljs-string">'\\\\?\\pipe'</span>, process.<span class="hljs-title function_">cwd</span>(), <span class="hljs-string">'myctl'</span>));</code> <button class="copy-button">copy</button></pre>
</section><section><h3>Class: <code>net.BlockList</code><span><a class="mark" href="#class-netblocklist" id="class-netblocklist">#</a></span><a aria-hidden="true" class="legacy" id="net_class_net_blocklist"></a></h3>
<div class="api_metadata">
<span>Added in: v15.0.0, v14.18.0</span>
</div>
<p>The <code>BlockList</code> object can be used with some network APIs to specify rules for
disabling inbound or outbound access to specific IP addresses, IP ranges, or
IP subnets.</p>
<h4><code>blockList.addAddress(address[, type])</code><span><a class="mark" href="#blocklistaddaddressaddress-type" id="blocklistaddaddressaddress-type">#</a></span><a aria-hidden="true" class="legacy" id="net_blocklist_addaddress_address_type"></a></h4>
<div class="api_metadata">
<span>Added in: v15.0.0, v14.18.0</span>
</div>
<ul>
<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="net.html#class-netsocketaddress" class="type"><net.SocketAddress></a> An IPv4 or IPv6 address.</li>
<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'ipv4'</code> or <code>'ipv6'</code>. <strong>Default:</strong> <code>'ipv4'</code>.</li>
</ul>
<p>Adds a rule to block the given IP address.</p>
<h4><code>blockList.addRange(start, end[, type])</code><span><a class="mark" href="#blocklistaddrangestart-end-type" id="blocklistaddrangestart-end-type">#</a></span><a aria-hidden="true" class="legacy" id="net_blocklist_addrange_start_end_type"></a></h4>
<div class="api_metadata">
<span>Added in: v15.0.0, v14.18.0</span>
</div>
<ul>
<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="net.html#class-netsocketaddress" class="type"><net.SocketAddress></a> The starting IPv4 or IPv6 address in the
range.</li>
<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="net.html#class-netsocketaddress" class="type"><net.SocketAddress></a> The ending IPv4 or IPv6 address in the range.</li>
<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'ipv4'</code> or <code>'ipv6'</code>. <strong>Default:</strong> <code>'ipv4'</code>.</li>
</ul>
<p>Adds a rule to block a range of IP addresses from <code>start</code> (inclusive) to
<code>end</code> (inclusive).</p>
<h4><code>blockList.addSubnet(net, prefix[, type])</code><span><a class="mark" href="#blocklistaddsubnetnet-prefix-type" id="blocklistaddsubnetnet-prefix-type">#</a></span><a aria-hidden="true" class="legacy" id="net_blocklist_addsubnet_net_prefix_type"></a></h4>
<div class="api_metadata">
<span>Added in: v15.0.0, v14.18.0</span>
</div>
<ul>
<li><code>net</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="net.html#class-netsocketaddress" class="type"><net.SocketAddress></a> The network IPv4 or IPv6 address.</li>
<li><code>prefix</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of CIDR prefix bits. For IPv4, this
must be a value between <code>0</code> and <code>32</code>. For IPv6, this must be between
<code>0</code> and <code>128</code>.</li>
<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'ipv4'</code> or <code>'ipv6'</code>. <strong>Default:</strong> <code>'ipv4'</code>.</li>
</ul>
<p>Adds a rule to block a range of IP addresses specified as a subnet mask.</p>
<h4><code>blockList.check(address[, type])</code><span><a class="mark" href="#blocklistcheckaddress-type" id="blocklistcheckaddress-type">#</a></span><a aria-hidden="true" class="legacy" id="net_blocklist_check_address_type"></a></h4>
<div class="api_metadata">
<span>Added in: v15.0.0, v14.18.0</span>
</div>
<ul>
<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="net.html#class-netsocketaddress" class="type"><net.SocketAddress></a> The IP address to check</li>
<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'ipv4'</code> or <code>'ipv6'</code>. <strong>Default:</strong> <code>'ipv4'</code>.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Returns <code>true</code> if the given IP address matches any of the rules added to the
<code>BlockList</code>.</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> blockList = <span class="hljs-keyword">new</span> net.<span class="hljs-title class_">BlockList</span>();
blockList.<span class="hljs-title function_">addAddress</span>(<span class="hljs-string">'123.123.123.123'</span>);
blockList.<span class="hljs-title function_">addRange</span>(<span class="hljs-string">'10.0.0.1'</span>, <span class="hljs-string">'10.0.0.10'</span>);
blockList.<span class="hljs-title function_">addSubnet</span>(<span class="hljs-string">'8592:757c:efae:4e45::'</span>, <span class="hljs-number">64</span>, <span class="hljs-string">'ipv6'</span>);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(blockList.<span class="hljs-title function_">check</span>(<span class="hljs-string">'123.123.123.123'</span>)); <span class="hljs-comment">// Prints: true</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(blockList.<span class="hljs-title function_">check</span>(<span class="hljs-string">'10.0.0.3'</span>)); <span class="hljs-comment">// Prints: true</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(blockList.<span class="hljs-title function_">check</span>(<span class="hljs-string">'222.111.111.222'</span>)); <span class="hljs-comment">// Prints: false</span>
<span class="hljs-comment">// IPv6 notation for IPv4 addresses works:</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(blockList.<span class="hljs-title function_">check</span>(<span class="hljs-string">'::ffff:7b7b:7b7b'</span>, <span class="hljs-string">'ipv6'</span>)); <span class="hljs-comment">// Prints: true</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(blockList.<span class="hljs-title function_">check</span>(<span class="hljs-string">'::ffff:123.123.123.123'</span>, <span class="hljs-string">'ipv6'</span>)); <span class="hljs-comment">// Prints: true</span></code> <button class="copy-button">copy</button></pre>
<h4><code>blockList.rules</code><span><a class="mark" href="#blocklistrules" id="blocklistrules">#</a></span><a aria-hidden="true" class="legacy" id="net_blocklist_rules"></a></h4>
<div class="api_metadata">
<span>Added in: v15.0.0, v14.18.0</span>
</div>
<ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li>
</ul>
<p>The list of rules added to the blocklist.</p>
</section><section><h3>Class: <code>net.SocketAddress</code><span><a class="mark" href="#class-netsocketaddress" id="class-netsocketaddress">#</a></span><a aria-hidden="true" class="legacy" id="net_class_net_socketaddress"></a></h3>
<div class="api_metadata">
<span>Added in: v15.14.0, v14.18.0</span>
</div>
<h4><code>new net.SocketAddress([options])</code><span><a class="mark" href="#new-netsocketaddressoptions" id="new-netsocketaddressoptions">#</a></span><a aria-hidden="true" class="legacy" id="net_new_net_socketaddress_options"></a></h4>
<div class="api_metadata">
<span>Added in: v15.14.0, v14.18.0</span>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
<ul>
<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The network address as either an IPv4 or IPv6 string.
<strong>Default</strong>: <code>'127.0.0.1'</code> if <code>family</code> is <code>'ipv4'</code>; <code>'::'</code> if <code>family</code> is
<code>'ipv6'</code>.</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> One of either <code>'ipv4'</code> or <code>'ipv6'</code>.
<strong>Default</strong>: <code>'ipv4'</code>.</li>
<li><code>flowlabel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> An IPv6 flow-label used only if <code>family</code> is <code>'ipv6'</code>.</li>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> An IP port.</li>
</ul>
</li>
</ul>
<h4><code>socketaddress.address</code><span><a class="mark" href="#socketaddressaddress" id="socketaddressaddress">#</a></span><a aria-hidden="true" class="legacy" id="net_socketaddress_address"></a></h4>
<div class="api_metadata">
<span>Added in: v15.14.0, v14.18.0</span>
</div>
<ul>
<li>Type <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<h4><code>socketaddress.family</code><span><a class="mark" href="#socketaddressfamily" id="socketaddressfamily">#</a></span><a aria-hidden="true" class="legacy" id="net_socketaddress_family"></a></h4>
<div class="api_metadata">
<span>Added in: v15.14.0, v14.18.0</span>
</div>
<ul>
<li>Type <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'ipv4'</code> or <code>'ipv6'</code>.</li>
</ul>
<h4><code>socketaddress.flowlabel</code><span><a class="mark" href="#socketaddressflowlabel" id="socketaddressflowlabel">#</a></span><a aria-hidden="true" class="legacy" id="net_socketaddress_flowlabel"></a></h4>
<div class="api_metadata">
<span>Added in: v15.14.0, v14.18.0</span>
</div>
<ul>
<li>Type <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<h4><code>socketaddress.port</code><span><a class="mark" href="#socketaddressport" id="socketaddressport">#</a></span><a aria-hidden="true" class="legacy" id="net_socketaddress_port"></a></h4>
<div class="api_metadata">
<span>Added in: v15.14.0, v14.18.0</span>
</div>
<ul>
<li>Type <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</section><section><h3>Class: <code>net.Server</code><span><a class="mark" href="#class-netserver" id="class-netserver">#</a></span><a aria-hidden="true" class="legacy" id="net_class_net_server"></a></h3>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li>Extends: <a href="events.html#class-eventemitter" class="type"><EventEmitter></a></li>
</ul>
<p>This class is used to create a TCP or <a href="#ipc-support">IPC</a> server.</p>
<h4><code>new net.Server([options][, connectionListener])</code><span><a class="mark" href="#new-netserveroptions-connectionlistener" id="new-netserveroptions-connectionlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_new_net_server_options_connectionlistener"></a></h4>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> See
<a href="#netcreateserveroptions-connectionlistener"><code>net.createServer([options][, connectionListener])</code></a>.</li>
<li><code>connectionListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Automatically set as a listener for the
<a href="#event-connection"><code>'connection'</code></a> event.</li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p><code>net.Server</code> is an <a href="events.html#class-eventemitter"><code>EventEmitter</code></a> with the following events:</p>
<h4>Event: <code>'close'</code><span><a class="mark" href="#event-close" id="event-close">#</a></span><a aria-hidden="true" class="legacy" id="net_event_close"></a></h4>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div>
<p>Emitted when the server closes. If connections exist, this
event is not emitted until all connections are ended.</p>
<h4>Event: <code>'connection'</code><span><a class="mark" href="#event-connection" id="event-connection">#</a></span><a aria-hidden="true" class="legacy" id="net_event_connection"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><a href="net.html#class-netsocket" class="type"><net.Socket></a> The connection object</li>
</ul>
<p>Emitted when a new connection is made. <code>socket</code> is an instance of
<code>net.Socket</code>.</p>
<h4>Event: <code>'error'</code><span><a class="mark" href="#event-error" id="event-error">#</a></span><a aria-hidden="true" class="legacy" id="net_event_error"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li>
</ul>
<p>Emitted when an error occurs. Unlike <a href="#class-netsocket"><code>net.Socket</code></a>, the <a href="#event-close"><code>'close'</code></a>
event will <strong>not</strong> be emitted directly following this event unless
<a href="#serverclosecallback"><code>server.close()</code></a> is manually called. See the example in discussion of
<a href="#serverlisten"><code>server.listen()</code></a>.</p>
<h4>Event: <code>'listening'</code><span><a class="mark" href="#event-listening" id="event-listening">#</a></span><a aria-hidden="true" class="legacy" id="net_event_listening"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<p>Emitted when the server has been bound after calling <a href="#serverlisten"><code>server.listen()</code></a>.</p>
<h4>Event: <code>'drop'</code><span><a class="mark" href="#event-drop" id="event-drop">#</a></span><a aria-hidden="true" class="legacy" id="net_event_drop"></a></h4>
<div class="api_metadata">
<span>Added in: v18.6.0, v16.17.0</span>
</div>
<p>When the number of connections reaches the threshold of <code>server.maxConnections</code>,
the server will drop new connections and emit <code>'drop'</code> event instead. If it is a
TCP server, the argument is as follows, otherwise the argument is <code>undefined</code>.</p>
<ul>
<li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The argument passed to event listener.
<ul>
<li><code>localAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Local address.</li>
<li><code>localPort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Local port.</li>
<li><code>localFamily</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Local family.</li>
<li><code>remoteAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Remote address.</li>
<li><code>remotePort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Remote port.</li>
<li><code>remoteFamily</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Remote IP family. <code>'IPv4'</code> or <code>'IPv6'</code>.</li>
</ul>
</li>
</ul>
<h4><code>server.address()</code><span><a class="mark" href="#serveraddress" id="serveraddress">#</a></span><a aria-hidden="true" class="legacy" id="net_server_address"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.4.0</td>
<td><p>The <code>family</code> property now returns a string instead of a number.</p></td></tr>
<tr><td>v18.0.0</td>
<td><p>The <code>family</code> property now returns a number instead of a string.</p></td></tr>
<tr><td>v0.1.90</td>
<td><p><span>Added in: v0.1.90</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a></li>
</ul>
<p>Returns the bound <code>address</code>, the address <code>family</code> name, and <code>port</code> of the server
as reported by the operating system if listening on an IP socket
(useful to find which port was assigned when getting an OS-assigned address):
<code>{ port: 12346, family: 'IPv4', address: '127.0.0.1' }</code>.</p>
<p>For a server listening on a pipe or Unix domain socket, the name is returned
as a string.</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> server = net.<span class="hljs-title function_">createServer</span>(<span class="hljs-function">(<span class="hljs-params">socket</span>) =></span> {
socket.<span class="hljs-title function_">end</span>(<span class="hljs-string">'goodbye\n'</span>);
}).<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> {
<span class="hljs-comment">// Handle errors here.</span>
<span class="hljs-keyword">throw</span> err;
});
<span class="hljs-comment">// Grab an arbitrary unused port.</span>
server.<span class="hljs-title function_">listen</span>(<span class="hljs-function">() =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'opened server on'</span>, server.<span class="hljs-title function_">address</span>());
});</code> <button class="copy-button">copy</button></pre>
<p><code>server.address()</code> returns <code>null</code> before the <code>'listening'</code> event has been
emitted or after calling <code>server.close()</code>.</p>
<h4><code>server.close([callback])</code><span><a class="mark" href="#serverclosecallback" id="serverclosecallback">#</a></span><a aria-hidden="true" class="legacy" id="net_server_close_callback"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called when the server is closed.</li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Stops the server from accepting new connections and keeps existing
connections. This function is asynchronous, the server is finally closed
when all connections are ended and the server emits a <a href="#event-close"><code>'close'</code></a> event.
The optional <code>callback</code> will be called once the <code>'close'</code> event occurs. Unlike
that event, it will be called with an <code>Error</code> as its only argument if the server
was not open when it was closed.</p>
<h4><code>server[Symbol.asyncDispose]()</code><span><a class="mark" href="#serversymbolasyncdispose" id="serversymbolasyncdispose">#</a></span><a aria-hidden="true" class="legacy" id="net_server_symbol_asyncdispose"></a></h4>
<div class="api_metadata">
<span>Added in: v20.5.0</span>
</div>
<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p>
<p>Calls <a href="#serverclosecallback"><code>server.close()</code></a> and returns a promise that fulfills when the
server has closed.</p>
<h4><code>server.getConnections(callback)</code><span><a class="mark" href="#servergetconnectionscallback" id="servergetconnectionscallback">#</a></span><a aria-hidden="true" class="legacy" id="net_server_getconnections_callback"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.7</span>
</div>
<ul>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Asynchronously get the number of concurrent connections on the server. Works
when sockets were sent to forks.</p>
<p>Callback should take two arguments <code>err</code> and <code>count</code>.</p>
<h4><code>server.listen()</code><span><a class="mark" href="#serverlisten" id="serverlisten">#</a></span><a aria-hidden="true" class="legacy" id="net_server_listen"></a></h4>
<p>Start a server listening for connections. A <code>net.Server</code> can be a TCP or
an <a href="#ipc-support">IPC</a> server depending on what it listens to.</p>
<p>Possible signatures:</p>
<ul>
<li><a href="#serverlistenhandle-backlog-callback"><code>server.listen(handle[, backlog][, callback])</code></a></li>
<li><a href="#serverlistenoptions-callback"><code>server.listen(options[, callback])</code></a></li>
<li><a href="#serverlistenpath-backlog-callback"><code>server.listen(path[, backlog][, callback])</code></a>
for <a href="#ipc-support">IPC</a> servers</li>
<li><a href="#serverlistenport-host-backlog-callback"><code>server.listen([port[, host[, backlog]]][, callback])</code></a>
for TCP servers</li>
</ul>
<p>This function is asynchronous. When the server starts listening, the
<a href="#event-listening"><code>'listening'</code></a> event will be emitted. The last parameter <code>callback</code>
will be added as a listener for the <a href="#event-listening"><code>'listening'</code></a> event.</p>
<p>All <code>listen()</code> methods can take a <code>backlog</code> parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as <code>tcp_max_syn_backlog</code> and <code>somaxconn</code>
on Linux. The default value of this parameter is 511 (not 512).</p>
<p>All <a href="#class-netsocket"><code>net.Socket</code></a> are set to <code>SO_REUSEADDR</code> (see <a href="https://man7.org/linux/man-pages/man7/socket.7.html"><code>socket(7)</code></a> for
details).</p>
<p>The <code>server.listen()</code> method can be called again if and only if there was an
error during the first <code>server.listen()</code> call or <code>server.close()</code> has been
called. Otherwise, an <code>ERR_SERVER_ALREADY_LISTEN</code> error will be thrown.</p>
<p>One of the most common errors raised when listening is <code>EADDRINUSE</code>.
This happens when another server is already listening on the requested
<code>port</code>/<code>path</code>/<code>handle</code>. One way to handle this would be to retry
after a certain amount of time:</p>
<pre><code class="language-js">server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">e</span>) =></span> {
<span class="hljs-keyword">if</span> (e.<span class="hljs-property">code</span> === <span class="hljs-string">'EADDRINUSE'</span>) {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">'Address in use, retrying...'</span>);
<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> {
server.<span class="hljs-title function_">close</span>();
server.<span class="hljs-title function_">listen</span>(<span class="hljs-variable constant_">PORT</span>, <span class="hljs-variable constant_">HOST</span>);
}, <span class="hljs-number">1000</span>);
}
});</code> <button class="copy-button">copy</button></pre>
<h5><code>server.listen(handle[, backlog][, callback])</code><span><a class="mark" href="#serverlistenhandle-backlog-callback" id="serverlistenhandle-backlog-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_server_listen_handle_backlog_callback"></a></h5>
<div class="api_metadata">
<span>Added in: v0.5.10</span>
</div>
<ul>
<li><code>handle</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
<li><code>backlog</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Common parameter of <a href="#serverlisten"><code>server.listen()</code></a> functions</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Start a server listening for connections on a given <code>handle</code> that has
already been bound to a port, a Unix domain socket, or a Windows named pipe.</p>
<p>The <code>handle</code> object can be either a server, a socket (anything with an
underlying <code>_handle</code> member), or an object with an <code>fd</code> member that is a
valid file descriptor.</p>
<p>Listening on a file descriptor is not supported on Windows.</p>
<h5><code>server.listen(options[, callback])</code><span><a class="mark" href="#serverlistenoptions-callback" id="serverlistenoptions-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_server_listen_options_callback"></a></h5>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v15.6.0</td>
<td><p>AbortSignal support was added.</p></td></tr>
<tr><td>v11.4.0</td>
<td><p>The <code>ipv6Only</code> option is supported.</p></td></tr>
<tr><td>v0.11.14</td>
<td><p><span>Added in: v0.11.14</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Required. Supports the following properties:
<ul>
<li><code>backlog</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Common parameter of <a href="#serverlisten"><code>server.listen()</code></a>
functions.</li>
<li><code>exclusive</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <strong>Default:</strong> <code>false</code></li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li><code>ipv6Only</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> For TCP servers, setting <code>ipv6Only</code> to <code>true</code> will
disable dual-stack support, i.e., binding to host <code>::</code> won't make
<code>0.0.0.0</code> be bound. <strong>Default:</strong> <code>false</code>.</li>
<li><code>path</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Will be ignored if <code>port</code> is specified. See
<a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a>.</li>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
<li><code>readableAll</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> For IPC servers makes the pipe readable
for all users. <strong>Default:</strong> <code>false</code>.</li>
<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> An AbortSignal that may be used to close a listening
server.</li>
<li><code>writableAll</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> For IPC servers makes the pipe writable
for all users. <strong>Default:</strong> <code>false</code>.</li>
</ul>
</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a>
functions.</li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>If <code>port</code> is specified, it behaves the same as
<a href="#serverlistenport-host-backlog-callback"><code>server.listen([port[, host[, backlog]]][, callback])</code></a>.
Otherwise, if <code>path</code> is specified, it behaves the same as
<a href="#serverlistenpath-backlog-callback"><code>server.listen(path[, backlog][, callback])</code></a>.
If none of them is specified, an error will be thrown.</p>
<p>If <code>exclusive</code> is <code>false</code> (default), then cluster workers will use the same
underlying handle, allowing connection handling duties to be shared. When
<code>exclusive</code> is <code>true</code>, the handle is not shared, and attempted port sharing
results in an error. An example which listens on an exclusive port is
shown below.</p>
<pre><code class="language-js">server.<span class="hljs-title function_">listen</span>({
<span class="hljs-attr">host</span>: <span class="hljs-string">'localhost'</span>,
<span class="hljs-attr">port</span>: <span class="hljs-number">80</span>,
<span class="hljs-attr">exclusive</span>: <span class="hljs-literal">true</span>,
});</code> <button class="copy-button">copy</button></pre>
<p>When <code>exclusive</code> is <code>true</code> and the underlying handle is shared, it is
possible that several workers query a handle with different backlogs.
In this case, the first <code>backlog</code> passed to the master process will be used.</p>
<p>Starting an IPC server as root may cause the server path to be inaccessible for
unprivileged users. Using <code>readableAll</code> and <code>writableAll</code> will make the server
accessible for all users.</p>
<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding
<code>AbortController</code> is similar to calling <code>.close()</code> on the server:</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> controller = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AbortController</span>();
server.<span class="hljs-title function_">listen</span>({
<span class="hljs-attr">host</span>: <span class="hljs-string">'localhost'</span>,
<span class="hljs-attr">port</span>: <span class="hljs-number">80</span>,
<span class="hljs-attr">signal</span>: controller.<span class="hljs-property">signal</span>,
});
<span class="hljs-comment">// Later, when you want to close the server.</span>
controller.<span class="hljs-title function_">abort</span>();</code> <button class="copy-button">copy</button></pre>
<h5><code>server.listen(path[, backlog][, callback])</code><span><a class="mark" href="#serverlistenpath-backlog-callback" id="serverlistenpath-backlog-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_server_listen_path_backlog_callback"></a></h5>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>path</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Path the server should listen to. See
<a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a>.</li>
<li><code>backlog</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Common parameter of <a href="#serverlisten"><code>server.listen()</code></a> functions.</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a>.</li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Start an <a href="#ipc-support">IPC</a> server listening for connections on the given <code>path</code>.</p>
<h5><code>server.listen([port[, host[, backlog]]][, callback])</code><span><a class="mark" href="#serverlistenport-host-backlog-callback" id="serverlistenport-host-backlog-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_server_listen_port_host_backlog_callback"></a></h5>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li><code>backlog</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Common parameter of <a href="#serverlisten"><code>server.listen()</code></a> functions.</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a>.</li>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Start a TCP server listening for connections on the given <code>port</code> and <code>host</code>.</p>
<p>If <code>port</code> is omitted or is 0, the operating system will assign an arbitrary
unused port, which can be retrieved by using <code>server.address().port</code>
after the <a href="#event-listening"><code>'listening'</code></a> event has been emitted.</p>
<p>If <code>host</code> is omitted, the server will accept connections on the
<a href="https://en.wikipedia.org/wiki/IPv6_address#Unspecified_address">unspecified IPv6 address</a> (<code>::</code>) when IPv6 is available, or the
<a href="https://en.wikipedia.org/wiki/0.0.0.0">unspecified IPv4 address</a> (<code>0.0.0.0</code>) otherwise.</p>
<p>In most operating systems, listening to the <a href="https://en.wikipedia.org/wiki/IPv6_address#Unspecified_address">unspecified IPv6 address</a> (<code>::</code>)
may cause the <code>net.Server</code> to also listen on the <a href="https://en.wikipedia.org/wiki/0.0.0.0">unspecified IPv4 address</a>
(<code>0.0.0.0</code>).</p>
<h4><code>server.listening</code><span><a class="mark" href="#serverlistening" id="serverlistening">#</a></span><a aria-hidden="true" class="legacy" id="net_server_listening"></a></h4>
<div class="api_metadata">
<span>Added in: v5.7.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Indicates whether or not the server is listening for connections.</li>
</ul>
<h4><code>server.maxConnections</code><span><a class="mark" href="#servermaxconnections" id="servermaxconnections">#</a></span><a aria-hidden="true" class="legacy" id="net_server_maxconnections"></a></h4>
<div class="api_metadata">
<span>Added in: v0.2.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Set this property to reject connections when the server's connection count gets
high.</p>
<p>It is not recommended to use this option once a socket has been sent to a child
with <a href="child_process.html#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>.</p>
<h4><code>server.ref()</code><span><a class="mark" href="#serverref" id="serverref">#</a></span><a aria-hidden="true" class="legacy" id="net_server_ref"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.1</span>
</div>
<ul>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Opposite of <code>unref()</code>, calling <code>ref()</code> on a previously <code>unref</code>ed server will
<em>not</em> let the program exit if it's the only server left (the default behavior).
If the server is <code>ref</code>ed calling <code>ref()</code> again will have no effect.</p>
<h4><code>server.unref()</code><span><a class="mark" href="#serverunref" id="serverunref">#</a></span><a aria-hidden="true" class="legacy" id="net_server_unref"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.1</span>
</div>
<ul>
<li>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></li>
</ul>
<p>Calling <code>unref()</code> on a server will allow the program to exit if this is the only
active server in the event system. If the server is already <code>unref</code>ed calling
<code>unref()</code> again will have no effect.</p>
</section><section><h3>Class: <code>net.Socket</code><span><a class="mark" href="#class-netsocket" id="class-netsocket">#</a></span><a aria-hidden="true" class="legacy" id="net_class_net_socket"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.4</span>
</div>
<ul>
<li>Extends: <a href="stream.html#class-streamduplex" class="type"><stream.Duplex></a></li>
</ul>
<p>This class is an abstraction of a TCP socket or a streaming <a href="#ipc-support">IPC</a> endpoint
(uses named pipes on Windows, and Unix domain sockets otherwise). It is also
an <a href="events.html#class-eventemitter"><code>EventEmitter</code></a>.</p>
<p>A <code>net.Socket</code> can be created by the user and used directly to interact with
a server. For example, it is returned by <a href="#netcreateconnection"><code>net.createConnection()</code></a>,
so the user can use it to talk to the server.</p>
<p>It can also be created by Node.js and passed to the user when a connection
is received. For example, it is passed to the listeners of a
<a href="#event-connection"><code>'connection'</code></a> event emitted on a <a href="#class-netserver"><code>net.Server</code></a>, so the user can use
it to interact with the client.</p>
<h4><code>new net.Socket([options])</code><span><a class="mark" href="#new-netsocketoptions" id="new-netsocketoptions">#</a></span><a aria-hidden="true" class="legacy" id="net_new_net_socket_options"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v15.14.0</td>
<td><p>AbortSignal support was added.</p></td></tr>
<tr><td>v0.3.4</td>
<td><p><span>Added in: v0.3.4</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Available options are:
<ul>
<li><code>allowHalfOpen</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to <code>false</code>, then the socket will
automatically end the writable side when the readable side ends. See
<a href="#netcreateserveroptions-connectionlistener"><code>net.createServer()</code></a> and the <a href="#event-end"><code>'end'</code></a> event for details. <strong>Default:</strong>
<code>false</code>.</li>
<li><code>fd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> If specified, wrap around an existing socket with
the given file descriptor, otherwise a new socket will be created.</li>
<li><code>onread</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> If specified, incoming data is stored in a single <code>buffer</code>
and passed to the supplied <code>callback</code> when data arrives on the socket.
This will cause the streaming functionality to not provide any data.
The socket will emit events like <code>'error'</code>, <code>'end'</code>, and <code>'close'</code>
as usual. Methods like <code>pause()</code> and <code>resume()</code> will also behave as
expected.
<ul>
<li><code>buffer</code> <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Either a reusable chunk of memory to
use for storing incoming data or a function that returns such.</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> This function is called for every chunk of incoming
data. Two arguments are passed to it: the number of bytes written to
<code>buffer</code> and a reference to <code>buffer</code>. Return <code>false</code> from this function to
implicitly <code>pause()</code> the socket. This function will be executed in the
global context.</li>
</ul>
</li>
<li><code>readable</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Allow reads on the socket when an <code>fd</code> is passed,
otherwise ignored. <strong>Default:</strong> <code>false</code>.</li>
<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> An Abort signal that may be used to destroy the
socket.</li>
<li><code>writable</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Allow writes on the socket when an <code>fd</code> is passed,
otherwise ignored. <strong>Default:</strong> <code>false</code>.</li>
</ul>
</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a></li>
</ul>
<p>Creates a new socket object.</p>
<p>The newly created socket can be either a TCP socket or a streaming <a href="#ipc-support">IPC</a>
endpoint, depending on what it <a href="#socketconnect"><code>connect()</code></a> to.</p>
<h4>Event: <code>'close'</code><span><a class="mark" href="#event-close_1" id="event-close_1">#</a></span><a aria-hidden="true" class="legacy" id="net_event_close_1"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>hadError</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if the socket had a transmission error.</li>
</ul>
<p>Emitted once the socket is fully closed. The argument <code>hadError</code> is a boolean
which says if the socket was closed due to a transmission error.</p>
<h4>Event: <code>'connect'</code><span><a class="mark" href="#event-connect" id="event-connect">#</a></span><a aria-hidden="true" class="legacy" id="net_event_connect"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<p>Emitted when a socket connection is successfully established.
See <a href="#netcreateconnection"><code>net.createConnection()</code></a>.</p>
<h4>Event: <code>'connectionAttempt'</code><span><a class="mark" href="#event-connectionattempt" id="event-connectionattempt">#</a></span><a aria-hidden="true" class="legacy" id="net_event_connectionattempt"></a></h4>
<div class="api_metadata">
<span>Added in: v20.12.0</span>
</div>
<ul>
<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The IP which the socket is attempting to connect to.</li>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The port which the socket is attempting to connect to.</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The family of the IP. It can be <code>6</code> for IPv6 or <code>4</code> for IPv4.</li>
</ul>
<p>Emitted when a new connection attempt is started. This may be emitted multiple times
if the family autoselection algorithm is enabled in <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.</p>
<h4>Event: <code>'connectionAttemptFailed'</code><span><a class="mark" href="#event-connectionattemptfailed" id="event-connectionattemptfailed">#</a></span><a aria-hidden="true" class="legacy" id="net_event_connectionattemptfailed"></a></h4>
<div class="api_metadata">
<span>Added in: v20.12.0</span>
</div>
<ul>
<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The IP which the socket attempted to connect to.</li>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The port which the socket attempted to connect to.</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The family of the IP. It can be <code>6</code> for IPv6 or <code>4</code> for IPv4.</li>
<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> The error associated with the failure.</li>
</ul>
<p>Emitted when a connection attempt failed. This may be emitted multiple times
if the family autoselection algorithm is enabled in <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.</p>
<h4>Event: <code>'connectionAttemptTimeout'</code><span><a class="mark" href="#event-connectionattempttimeout" id="event-connectionattempttimeout">#</a></span><a aria-hidden="true" class="legacy" id="net_event_connectionattempttimeout"></a></h4>
<div class="api_metadata">
<span>Added in: v20.12.0</span>
</div>
<ul>
<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The IP which the socket attempted to connect to.</li>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The port which the socket attempted to connect to.</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The family of the IP. It can be <code>6</code> for IPv6 or <code>4</code> for IPv4.</li>
</ul>
<p>Emitted when a connection attempt timed out. This is only emitted (and may be
emitted multiple times) if the family autoselection algorithm is enabled
in <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.</p>
<h4>Event: <code>'data'</code><span><a class="mark" href="#event-data" id="event-data">#</a></span><a aria-hidden="true" class="legacy" id="net_event_data"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Emitted when data is received. The argument <code>data</code> will be a <code>Buffer</code> or
<code>String</code>. Encoding of data is set by <a href="#socketsetencodingencoding"><code>socket.setEncoding()</code></a>.</p>
<p>The data will be lost if there is no listener when a <code>Socket</code>
emits a <code>'data'</code> event.</p>
<h4>Event: <code>'drain'</code><span><a class="mark" href="#event-drain" id="event-drain">#</a></span><a aria-hidden="true" class="legacy" id="net_event_drain"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<p>Emitted when the write buffer becomes empty. Can be used to throttle uploads.</p>
<p>See also: the return values of <code>socket.write()</code>.</p>
<h4>Event: <code>'end'</code><span><a class="mark" href="#event-end" id="event-end">#</a></span><a aria-hidden="true" class="legacy" id="net_event_end"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<p>Emitted when the other end of the socket signals the end of transmission, thus
ending the readable side of the socket.</p>
<p>By default (<code>allowHalfOpen</code> is <code>false</code>) the socket will send an end of
transmission packet back and destroy its file descriptor once it has written out
its pending write queue. However, if <code>allowHalfOpen</code> is set to <code>true</code>, the
socket will not automatically <a href="#socketenddata-encoding-callback"><code>end()</code></a> its writable side,
allowing the user to write arbitrary amounts of data. The user must call
<a href="#socketenddata-encoding-callback"><code>end()</code></a> explicitly to close the connection (i.e. sending a
FIN packet back).</p>
<h4>Event: <code>'error'</code><span><a class="mark" href="#event-error_1" id="event-error_1">#</a></span><a aria-hidden="true" class="legacy" id="net_event_error_1"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li>
</ul>
<p>Emitted when an error occurs. The <code>'close'</code> event will be called directly
following this event.</p>
<h4>Event: <code>'lookup'</code><span><a class="mark" href="#event-lookup" id="event-lookup">#</a></span><a aria-hidden="true" class="legacy" id="net_event_lookup"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v5.10.0</td>
<td><p>The <code>host</code> parameter is supported now.</p></td></tr>
<tr><td>v0.11.3</td>
<td><p><span>Added in: v0.11.3</span></p></td></tr>
</tbody></table>
</details>
</div>
<p>Emitted after resolving the host name but before connecting.
Not applicable to Unix sockets.</p>
<ul>
<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> The error object. See <a href="dns.html#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>.</li>
<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The IP address.</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> The address type. See <a href="dns.html#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>.</li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The host name.</li>
</ul>
<h4>Event: <code>'ready'</code><span><a class="mark" href="#event-ready" id="event-ready">#</a></span><a aria-hidden="true" class="legacy" id="net_event_ready"></a></h4>
<div class="api_metadata">
<span>Added in: v9.11.0</span>
</div>
<p>Emitted when a socket is ready to be used.</p>
<p>Triggered immediately after <code>'connect'</code>.</p>
<h4>Event: <code>'timeout'</code><span><a class="mark" href="#event-timeout" id="event-timeout">#</a></span><a aria-hidden="true" class="legacy" id="net_event_timeout"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<p>Emitted if the socket times out from inactivity. This is only to notify that
the socket has been idle. The user must manually close the connection.</p>
<p>See also: <a href="#socketsettimeouttimeout-callback"><code>socket.setTimeout()</code></a>.</p>
<h4><code>socket.address()</code><span><a class="mark" href="#socketaddress" id="socketaddress">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_address"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.4.0</td>
<td><p>The <code>family</code> property now returns a string instead of a number.</p></td></tr>
<tr><td>v18.0.0</td>
<td><p>The <code>family</code> property now returns a number instead of a string.</p></td></tr>
<tr><td>v0.1.90</td>
<td><p><span>Added in: v0.1.90</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
</ul>
<p>Returns the bound <code>address</code>, the address <code>family</code> name and <code>port</code> of the
socket as reported by the operating system:
<code>{ port: 12346, family: 'IPv4', address: '127.0.0.1' }</code></p>
<h4><code>socket.autoSelectFamilyAttemptedAddresses</code><span><a class="mark" href="#socketautoselectfamilyattemptedaddresses" id="socketautoselectfamilyattemptedaddresses">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_autoselectfamilyattemptedaddresses"></a></h4>
<div class="api_metadata">
<span>Added in: v19.4.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li>
</ul>
<p>This property is only present if the family autoselection algorithm is enabled in
<a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a> and it is an array of the addresses that have been attempted.</p>
<p>Each address is a string in the form of <code>$IP:$PORT</code>. If the connection was successful,
then the last address is the one that the socket is currently connected to.</p>
<h4><code>socket.bufferSize</code><span><a class="mark" href="#socketbuffersize" id="socketbuffersize">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_buffersize"></a></h4>
<div class="api_metadata">
<span>Added in: v0.3.8</span><span>Deprecated since: v14.6.0</span>
</div>
<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated: Use <a href="stream.html#writablewritablelength"><code>writable.writableLength</code></a> instead.</div><p></p>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>This property shows the number of characters buffered for writing. The buffer
may contain strings whose length after encoding is not yet known. So this number
is only an approximation of the number of bytes in the buffer.</p>
<p><code>net.Socket</code> has the property that <code>socket.write()</code> always works. This is to
help users get up and running quickly. The computer cannot always keep up
with the amount of data that is written to a socket. The network connection
simply might be too slow. Node.js will internally queue up the data written to a
socket and send it out over the wire when it is possible.</p>
<p>The consequence of this internal buffering is that memory may grow.
Users who experience large or growing <code>bufferSize</code> should attempt to
"throttle" the data flows in their program with
<a href="#socketpause"><code>socket.pause()</code></a> and <a href="#socketresume"><code>socket.resume()</code></a>.</p>
<h4><code>socket.bytesRead</code><span><a class="mark" href="#socketbytesread" id="socketbytesread">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_bytesread"></a></h4>
<div class="api_metadata">
<span>Added in: v0.5.3</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>The amount of received bytes.</p>
<h4><code>socket.bytesWritten</code><span><a class="mark" href="#socketbyteswritten" id="socketbyteswritten">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_byteswritten"></a></h4>
<div class="api_metadata">
<span>Added in: v0.5.3</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>The amount of bytes sent.</p>
<h4><code>socket.connect()</code><span><a class="mark" href="#socketconnect" id="socketconnect">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_connect"></a></h4>
<p>Initiate a connection on a given socket.</p>
<p>Possible signatures:</p>
<ul>
<li><a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a></li>
<li><a href="#socketconnectpath-connectlistener"><code>socket.connect(path[, connectListener])</code></a>
for <a href="#ipc-support">IPC</a> connections.</li>
<li><a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a>
for TCP connections.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>This function is asynchronous. When the connection is established, the
<a href="#event-connect"><code>'connect'</code></a> event will be emitted. If there is a problem connecting,
instead of a <a href="#event-connect"><code>'connect'</code></a> event, an <a href="#event-error_1"><code>'error'</code></a> event will be emitted with
the error passed to the <a href="#event-error_1"><code>'error'</code></a> listener.
The last parameter <code>connectListener</code>, if supplied, will be added as a listener
for the <a href="#event-connect"><code>'connect'</code></a> event <strong>once</strong>.</p>
<p>This function should only be used for reconnecting a socket after
<code>'close'</code> has been emitted or otherwise it may lead to undefined
behavior.</p>
<h5><code>socket.connect(options[, connectListener])</code><span><a class="mark" href="#socketconnectoptions-connectlistener" id="socketconnectoptions-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_connect_options_connectlistener"></a></h5>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v20.0.0</td>
<td><p>The default value for the autoSelectFamily option is now true. The <code>--enable-network-family-autoselection</code> CLI flag has been renamed to <code>--network-family-autoselection</code>. The old name is now an alias but it is discouraged.</p></td></tr>
<tr><td>v19.4.0</td>
<td><p>The default value for autoSelectFamily option can be changed at runtime using <code>setDefaultAutoSelectFamily</code> or via the command line option <code>--enable-network-family-autoselection</code>.</p></td></tr>
<tr><td>v19.3.0, v18.13.0</td>
<td><p>Added the <code>autoSelectFamily</code> option.</p></td></tr>
<tr><td>v17.7.0, v16.15.0</td>
<td><p>The <code>noDelay</code>, <code>keepAlive</code>, and <code>keepAliveInitialDelay</code> options are supported now.</p></td></tr>
<tr><td>v12.10.0</td>
<td><p>Added <code>onread</code> option.</p></td></tr>
<tr><td>v6.0.0</td>
<td><p>The <code>hints</code> option defaults to <code>0</code> in all cases now. Previously, in the absence of the <code>family</code> option it would default to <code>dns.ADDRCONFIG | dns.V4MAPPED</code>.</p></td></tr>
<tr><td>v5.11.0</td>
<td><p>The <code>hints</code> option is supported now.</p></td></tr>
<tr><td>v0.1.90</td>
<td><p><span>Added in: v0.1.90</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Common parameter of <a href="#socketconnect"><code>socket.connect()</code></a>
methods. Will be added as a listener for the <a href="#event-connect"><code>'connect'</code></a> event once.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Initiate a connection on a given socket. Normally this method is not needed,
the socket should be created and opened with <a href="#netcreateconnection"><code>net.createConnection()</code></a>. Use
this only when implementing a custom Socket.</p>
<p>For TCP connections, available <code>options</code> are:</p>
<ul>
<li><code>autoSelectFamily</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a>: If set to <code>true</code>, it enables a family
autodetection algorithm that loosely implements section 5 of <a href="https://www.rfc-editor.org/rfc/rfc8305.txt">RFC 8305</a>. The
<code>all</code> option passed to lookup is set to <code>true</code> and the sockets attempts to
connect to all obtained IPv6 and IPv4 addresses, in sequence, until a
connection is established. The first returned AAAA address is tried first,
then the first returned A address, then the second returned AAAA address and
so on. Each connection attempt (but the last one) is given the amount of time
specified by the <code>autoSelectFamilyAttemptTimeout</code> option before timing out and
trying the next address. Ignored if the <code>family</code> option is not <code>0</code> or if
<code>localAddress</code> is set. Connection errors are not emitted if at least one
connection succeeds. If all connections attempts fails, a single
<code>AggregateError</code> with all failed attempts is emitted. <strong>Default:</strong>
<a href="#netgetdefaultautoselectfamily"><code>net.getDefaultAutoSelectFamily()</code></a>.</li>
<li><code>autoSelectFamilyAttemptTimeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a>: The amount of time in milliseconds
to wait for a connection attempt to finish before trying the next address when
using the <code>autoSelectFamily</code> option. If set to a positive integer less than
<code>10</code>, then the value <code>10</code> will be used instead. <strong>Default:</strong>
<a href="#netgetdefaultautoselectfamilyattempttimeout"><code>net.getDefaultAutoSelectFamilyAttemptTimeout()</code></a>.</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a>: Version of IP stack. Must be <code>4</code>, <code>6</code>, or <code>0</code>. The value
<code>0</code> indicates that both IPv4 and IPv6 addresses are allowed. <strong>Default:</strong> <code>0</code>.</li>
<li><code>hints</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Optional <a href="dns.html#supported-getaddrinfo-flags"><code>dns.lookup()</code> hints</a>.</li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host the socket should connect to. <strong>Default:</strong> <code>'localhost'</code>.</li>
<li><code>keepAlive</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to <code>true</code>, it enables keep-alive functionality on
the socket immediately after the connection is established, similarly on what
is done in <a href="#socketsetkeepaliveenable-initialdelay"><code>socket.setKeepAlive()</code></a>. <strong>Default:</strong> <code>false</code>.</li>
<li><code>keepAliveInitialDelay</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> If set to a positive number, it sets the
initial delay before the first keepalive probe is sent on an idle socket.
<strong>Default:</strong> <code>0</code>.</li>
<li><code>localAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Local address the socket should connect from.</li>
<li><code>localPort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Local port the socket should connect from.</li>
<li><code>lookup</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Custom lookup function. <strong>Default:</strong> <a href="dns.html#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>.</li>
<li><code>noDelay</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to <code>true</code>, it disables the use of Nagle's algorithm
immediately after the socket is established. <strong>Default:</strong> <code>false</code>.</li>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Required. Port the socket should connect to.</li>
</ul>
<p>For <a href="#ipc-support">IPC</a> connections, available <code>options</code> are:</p>
<ul>
<li><code>path</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Required. Path the client should connect to.
See <a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a>. If provided, the TCP-specific
options above are ignored.</li>
</ul>
<h5><code>socket.connect(path[, connectListener])</code><span><a class="mark" href="#socketconnectpath-connectlistener" id="socketconnectpath-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_connect_path_connectlistener"></a></h5>
<ul>
<li><code>path</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Path the client should connect to. See
<a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a>.</li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Common parameter of <a href="#socketconnect"><code>socket.connect()</code></a>
methods. Will be added as a listener for the <a href="#event-connect"><code>'connect'</code></a> event once.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Initiate an <a href="#ipc-support">IPC</a> connection on the given socket.</p>
<p>Alias to
<a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a>
called with <code>{ path: path }</code> as <code>options</code>.</p>
<h5><code>socket.connect(port[, host][, connectListener])</code><span><a class="mark" href="#socketconnectport-host-connectlistener" id="socketconnectport-host-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_connect_port_host_connectlistener"></a></h5>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Port the client should connect to.</li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host the client should connect to.</li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Common parameter of <a href="#socketconnect"><code>socket.connect()</code></a>
methods. Will be added as a listener for the <a href="#event-connect"><code>'connect'</code></a> event once.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Initiate a TCP connection on the given socket.</p>
<p>Alias to
<a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a>
called with <code>{port: port, host: host}</code> as <code>options</code>.</p>
<h4><code>socket.connecting</code><span><a class="mark" href="#socketconnecting" id="socketconnecting">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_connecting"></a></h4>
<div class="api_metadata">
<span>Added in: v6.1.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>If <code>true</code>,
<a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a> was
called and has not yet finished. It will stay <code>true</code> until the socket becomes
connected, then it is set to <code>false</code> and the <code>'connect'</code> event is emitted. Note
that the
<a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a>
callback is a listener for the <code>'connect'</code> event.</p>
<h4><code>socket.destroy([error])</code><span><a class="mark" href="#socketdestroyerror" id="socketdestroyerror">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_destroy_error"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a></li>
</ul>
<p>Ensures that no more I/O activity happens on this socket.
Destroys the stream and closes the connection.</p>
<p>See <a href="stream.html#writabledestroyerror"><code>writable.destroy()</code></a> for further details.</p>
<h4><code>socket.destroyed</code><span><a class="mark" href="#socketdestroyed" id="socketdestroyed">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_destroyed"></a></h4>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Indicates if the connection is destroyed or not. Once a
connection is destroyed no further data can be transferred using it.</li>
</ul>
<p>See <a href="stream.html#writabledestroyed"><code>writable.destroyed</code></a> for further details.</p>
<h4><code>socket.destroySoon()</code><span><a class="mark" href="#socketdestroysoon" id="socketdestroysoon">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_destroysoon"></a></h4>
<div class="api_metadata">
<span>Added in: v0.3.4</span>
</div>
<p>Destroys the socket after all data is written. If the <code>'finish'</code> event was
already emitted the socket is destroyed immediately. If the socket is still
writable it implicitly calls <code>socket.end()</code>.</p>
<h4><code>socket.end([data[, encoding]][, callback])</code><span><a class="mark" href="#socketenddata-encoding-callback" id="socketenddata-encoding-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_end_data_encoding_callback"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Only used when data is <code>string</code>. <strong>Default:</strong> <code>'utf8'</code>.</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Optional callback for when the socket is finished.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Half-closes the socket. i.e., it sends a FIN packet. It is possible the
server will still send some data.</p>
<p>See <a href="stream.html#writableendchunk-encoding-callback"><code>writable.end()</code></a> for further details.</p>
<h4><code>socket.localAddress</code><span><a class="mark" href="#socketlocaladdress" id="socketlocaladdress">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_localaddress"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.6</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The string representation of the local IP address the remote client is
connecting on. For example, in a server listening on <code>'0.0.0.0'</code>, if a client
connects on <code>'192.168.1.1'</code>, the value of <code>socket.localAddress</code> would be
<code>'192.168.1.1'</code>.</p>
<h4><code>socket.localPort</code><span><a class="mark" href="#socketlocalport" id="socketlocalport">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_localport"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.6</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>The numeric representation of the local port. For example, <code>80</code> or <code>21</code>.</p>
<h4><code>socket.localFamily</code><span><a class="mark" href="#socketlocalfamily" id="socketlocalfamily">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_localfamily"></a></h4>
<div class="api_metadata">
<span>Added in: v18.8.0, v16.18.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The string representation of the local IP family. <code>'IPv4'</code> or <code>'IPv6'</code>.</p>
<h4><code>socket.pause()</code><span><a class="mark" href="#socketpause" id="socketpause">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_pause"></a></h4>
<ul>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Pauses the reading of data. That is, <a href="#event-data"><code>'data'</code></a> events will not be emitted.
Useful to throttle back an upload.</p>
<h4><code>socket.pending</code><span><a class="mark" href="#socketpending" id="socketpending">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_pending"></a></h4>
<div class="api_metadata">
<span>Added in: v11.2.0, v10.16.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>This is <code>true</code> if the socket is not connected yet, either because <code>.connect()</code>
has not yet been called or because it is still in the process of connecting
(see <a href="#socketconnecting"><code>socket.connecting</code></a>).</p>
<h4><code>socket.ref()</code><span><a class="mark" href="#socketref" id="socketref">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_ref"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.1</span>
</div>
<ul>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Opposite of <code>unref()</code>, calling <code>ref()</code> on a previously <code>unref</code>ed socket will
<em>not</em> let the program exit if it's the only socket left (the default behavior).
If the socket is <code>ref</code>ed calling <code>ref</code> again will have no effect.</p>
<h4><code>socket.remoteAddress</code><span><a class="mark" href="#socketremoteaddress" id="socketremoteaddress">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_remoteaddress"></a></h4>
<div class="api_metadata">
<span>Added in: v0.5.10</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The string representation of the remote IP address. For example,
<code>'74.125.127.100'</code> or <code>'2001:4860:a005::68'</code>. Value may be <code>undefined</code> if
the socket is destroyed (for example, if the client disconnected).</p>
<h4><code>socket.remoteFamily</code><span><a class="mark" href="#socketremotefamily" id="socketremotefamily">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_remotefamily"></a></h4>
<div class="api_metadata">
<span>Added in: v0.11.14</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The string representation of the remote IP family. <code>'IPv4'</code> or <code>'IPv6'</code>. Value may be <code>undefined</code> if
the socket is destroyed (for example, if the client disconnected).</p>
<h4><code>socket.remotePort</code><span><a class="mark" href="#socketremoteport" id="socketremoteport">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_remoteport"></a></h4>
<div class="api_metadata">
<span>Added in: v0.5.10</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>The numeric representation of the remote port. For example, <code>80</code> or <code>21</code>. Value may be <code>undefined</code> if
the socket is destroyed (for example, if the client disconnected).</p>
<h4><code>socket.resetAndDestroy()</code><span><a class="mark" href="#socketresetanddestroy" id="socketresetanddestroy">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_resetanddestroy"></a></h4>
<div class="api_metadata">
<span>Added in: v18.3.0, v16.17.0</span>
</div>
<ul>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a></li>
</ul>
<p>Close the TCP connection by sending an RST packet and destroy the stream.
If this TCP socket is in connecting status, it will send an RST packet and destroy this TCP socket once it is connected.
Otherwise, it will call <code>socket.destroy</code> with an <code>ERR_SOCKET_CLOSED</code> Error.
If this is not a TCP socket (for example, a pipe), calling this method will immediately throw an <code>ERR_INVALID_HANDLE_TYPE</code> Error.</p>
<h4><code>socket.resume()</code><span><a class="mark" href="#socketresume" id="socketresume">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_resume"></a></h4>
<ul>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Resumes reading after a call to <a href="#socketpause"><code>socket.pause()</code></a>.</p>
<h4><code>socket.setEncoding([encoding])</code><span><a class="mark" href="#socketsetencodingencoding" id="socketsetencodingencoding">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_setencoding_encoding"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Set the encoding for the socket as a <a href="stream.html#class-streamreadable">Readable Stream</a>. See
<a href="stream.html#readablesetencodingencoding"><code>readable.setEncoding()</code></a> for more information.</p>
<h4><code>socket.setKeepAlive([enable][, initialDelay])</code><span><a class="mark" href="#socketsetkeepaliveenable-initialdelay" id="socketsetkeepaliveenable-initialdelay">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_setkeepalive_enable_initialdelay"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v13.12.0, v12.17.0</td>
<td><p>New defaults for <code>TCP_KEEPCNT</code> and <code>TCP_KEEPINTVL</code> socket options were added.</p></td></tr>
<tr><td>v0.1.92</td>
<td><p><span>Added in: v0.1.92</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li><code>enable</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <strong>Default:</strong> <code>false</code></li>
<li><code>initialDelay</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> <strong>Default:</strong> <code>0</code></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Enable/disable keep-alive functionality, and optionally set the initial
delay before the first keepalive probe is sent on an idle socket.</p>
<p>Set <code>initialDelay</code> (in milliseconds) to set the delay between the last
data packet received and the first keepalive probe. Setting <code>0</code> for
<code>initialDelay</code> will leave the value unchanged from the default
(or previous) setting.</p>
<p>Enabling the keep-alive functionality will set the following socket options:</p>
<ul>
<li><code>SO_KEEPALIVE=1</code></li>
<li><code>TCP_KEEPIDLE=initialDelay</code></li>
<li><code>TCP_KEEPCNT=10</code></li>
<li><code>TCP_KEEPINTVL=1</code></li>
</ul>
<h4><code>socket.setNoDelay([noDelay])</code><span><a class="mark" href="#socketsetnodelaynodelay" id="socketsetnodelaynodelay">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_setnodelay_nodelay"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>noDelay</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <strong>Default:</strong> <code>true</code></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Enable/disable the use of Nagle's algorithm.</p>
<p>When a TCP connection is created, it will have Nagle's algorithm enabled.</p>
<p>Nagle's algorithm delays data before it is sent via the network. It attempts
to optimize throughput at the expense of latency.</p>
<p>Passing <code>true</code> for <code>noDelay</code> or not passing an argument will disable Nagle's
algorithm for the socket. Passing <code>false</code> for <code>noDelay</code> will enable Nagle's
algorithm.</p>
<h4><code>socket.setTimeout(timeout[, callback])</code><span><a class="mark" href="#socketsettimeouttimeout-callback" id="socketsettimeouttimeout-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_settimeout_timeout_callback"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr>
<tr><td>v0.1.90</td>
<td><p><span>Added in: v0.1.90</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Sets the socket to timeout after <code>timeout</code> milliseconds of inactivity on
the socket. By default <code>net.Socket</code> do not have a timeout.</p>
<p>When an idle timeout is triggered the socket will receive a <a href="#event-timeout"><code>'timeout'</code></a>
event but the connection will not be severed. The user must manually call
<a href="#socketenddata-encoding-callback"><code>socket.end()</code></a> or <a href="#socketdestroyerror"><code>socket.destroy()</code></a> to end the connection.</p>
<pre><code class="language-js">socket.<span class="hljs-built_in">setTimeout</span>(<span class="hljs-number">3000</span>);
socket.<span class="hljs-title function_">on</span>(<span class="hljs-string">'timeout'</span>, <span class="hljs-function">() =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'socket timeout'</span>);
socket.<span class="hljs-title function_">end</span>();
});</code> <button class="copy-button">copy</button></pre>
<p>If <code>timeout</code> is 0, then the existing idle timeout is disabled.</p>
<p>The optional <code>callback</code> parameter will be added as a one-time listener for the
<a href="#event-timeout"><code>'timeout'</code></a> event.</p>
<h4><code>socket.timeout</code><span><a class="mark" href="#sockettimeout" id="sockettimeout">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_timeout"></a></h4>
<div class="api_metadata">
<span>Added in: v10.7.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Undefined_type" class="type"><undefined></a></li>
</ul>
<p>The socket timeout in milliseconds as set by <a href="#socketsettimeouttimeout-callback"><code>socket.setTimeout()</code></a>.
It is <code>undefined</code> if a timeout has not been set.</p>
<h4><code>socket.unref()</code><span><a class="mark" href="#socketunref" id="socketunref">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_unref"></a></h4>
<div class="api_metadata">
<span>Added in: v0.9.1</span>
</div>
<ul>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The socket itself.</li>
</ul>
<p>Calling <code>unref()</code> on a socket will allow the program to exit if this is the only
active socket in the event system. If the socket is already <code>unref</code>ed calling
<code>unref()</code> again will have no effect.</p>
<h4><code>socket.write(data[, encoding][, callback])</code><span><a class="mark" href="#socketwritedata-encoding-callback" id="socketwritedata-encoding-callback">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_write_data_encoding_callback"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Only used when data is <code>string</code>. <strong>Default:</strong> <code>utf8</code>.</li>
<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Sends data on the socket. The second parameter specifies the encoding in the
case of a string. It defaults to UTF8 encoding.</p>
<p>Returns <code>true</code> if the entire data was flushed successfully to the kernel
buffer. Returns <code>false</code> if all or part of the data was queued in user memory.
<a href="#event-drain"><code>'drain'</code></a> will be emitted when the buffer is again free.</p>
<p>The optional <code>callback</code> parameter will be executed when the data is finally
written out, which may not be immediately.</p>
<p>See <code>Writable</code> stream <a href="stream.html#writablewritechunk-encoding-callback"><code>write()</code></a> method for more
information.</p>
<h4><code>socket.readyState</code><span><a class="mark" href="#socketreadystate" id="socketreadystate">#</a></span><a aria-hidden="true" class="legacy" id="net_socket_readystate"></a></h4>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>This property represents the state of the connection as a string.</p>
<ul>
<li>If the stream is connecting <code>socket.readyState</code> is <code>opening</code>.</li>
<li>If the stream is readable and writable, it is <code>open</code>.</li>
<li>If the stream is readable and not writable, it is <code>readOnly</code>.</li>
<li>If the stream is not readable and writable, it is <code>writeOnly</code>.</li>
</ul>
</section><section><h3><code>net.connect()</code><span><a class="mark" href="#netconnect" id="netconnect">#</a></span><a aria-hidden="true" class="legacy" id="net_net_connect"></a></h3>
<p>Aliases to
<a href="#netcreateconnection"><code>net.createConnection()</code></a>.</p>
<p>Possible signatures:</p>
<ul>
<li><a href="#netconnectoptions-connectlistener"><code>net.connect(options[, connectListener])</code></a></li>
<li><a href="#netconnectpath-connectlistener"><code>net.connect(path[, connectListener])</code></a> for <a href="#ipc-support">IPC</a>
connections.</li>
<li><a href="#netconnectport-host-connectlistener"><code>net.connect(port[, host][, connectListener])</code></a>
for TCP connections.</li>
</ul>
<h4><code>net.connect(options[, connectListener])</code><span><a class="mark" href="#netconnectoptions-connectlistener" id="netconnectoptions-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_connect_options_connectlistener"></a></h4>
<div class="api_metadata">
<span>Added in: v0.7.0</span>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a></li>
</ul>
<p>Alias to
<a href="#netcreateconnectionoptions-connectlistener"><code>net.createConnection(options[, connectListener])</code></a>.</p>
<h4><code>net.connect(path[, connectListener])</code><span><a class="mark" href="#netconnectpath-connectlistener" id="netconnectpath-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_connect_path_connectlistener"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>path</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a></li>
</ul>
<p>Alias to
<a href="#netcreateconnectionpath-connectlistener"><code>net.createConnection(path[, connectListener])</code></a>.</p>
<h4><code>net.connect(port[, host][, connectListener])</code><span><a class="mark" href="#netconnectport-host-connectlistener" id="netconnectport-host-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_connect_port_host_connectlistener"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a></li>
</ul>
<p>Alias to
<a href="#netcreateconnectionport-host-connectlistener"><code>net.createConnection(port[, host][, connectListener])</code></a>.</p>
</section><section><h3><code>net.createConnection()</code><span><a class="mark" href="#netcreateconnection" id="netcreateconnection">#</a></span><a aria-hidden="true" class="legacy" id="net_net_createconnection"></a></h3>
<p>A factory function, which creates a new <a href="#class-netsocket"><code>net.Socket</code></a>,
immediately initiates connection with <a href="#socketconnect"><code>socket.connect()</code></a>,
then returns the <code>net.Socket</code> that starts the connection.</p>
<p>When the connection is established, a <a href="#event-connect"><code>'connect'</code></a> event will be emitted
on the returned socket. The last parameter <code>connectListener</code>, if supplied,
will be added as a listener for the <a href="#event-connect"><code>'connect'</code></a> event <strong>once</strong>.</p>
<p>Possible signatures:</p>
<ul>
<li><a href="#netcreateconnectionoptions-connectlistener"><code>net.createConnection(options[, connectListener])</code></a></li>
<li><a href="#netcreateconnectionpath-connectlistener"><code>net.createConnection(path[, connectListener])</code></a>
for <a href="#ipc-support">IPC</a> connections.</li>
<li><a href="#netcreateconnectionport-host-connectlistener"><code>net.createConnection(port[, host][, connectListener])</code></a>
for TCP connections.</li>
</ul>
<p>The <a href="#netconnect"><code>net.connect()</code></a> function is an alias to this function.</p>
<h4><code>net.createConnection(options[, connectListener])</code><span><a class="mark" href="#netcreateconnectionoptions-connectlistener" id="netcreateconnectionoptions-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_createconnection_options_connectlistener"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Required. Will be passed to both the
<a href="#new-netsocketoptions"><code>new net.Socket([options])</code></a> call and the
<a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a>
method.</li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Common parameter of the
<a href="#netcreateconnection"><code>net.createConnection()</code></a> functions. If supplied, will be added as
a listener for the <a href="#event-connect"><code>'connect'</code></a> event on the returned socket once.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The newly created socket used to start the connection.</li>
</ul>
<p>For available options, see
<a href="#new-netsocketoptions"><code>new net.Socket([options])</code></a>
and <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options[, connectListener])</code></a>.</p>
<p>Additional options:</p>
<ul>
<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> If set, will be used to call
<a href="#socketsettimeouttimeout-callback"><code>socket.setTimeout(timeout)</code></a> after the socket is created, but before
it starts the connection.</li>
</ul>
<p>Following is an example of a client of the echo server described
in the <a href="#netcreateserveroptions-connectionlistener"><code>net.createServer()</code></a> section:</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> net = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>);
<span class="hljs-keyword">const</span> client = net.<span class="hljs-title function_">createConnection</span>({ <span class="hljs-attr">port</span>: <span class="hljs-number">8124</span> }, <span class="hljs-function">() =></span> {
<span class="hljs-comment">// 'connect' listener.</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'connected to server!'</span>);
client.<span class="hljs-title function_">write</span>(<span class="hljs-string">'world!\r\n'</span>);
});
client.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(data.<span class="hljs-title function_">toString</span>());
client.<span class="hljs-title function_">end</span>();
});
client.<span class="hljs-title function_">on</span>(<span class="hljs-string">'end'</span>, <span class="hljs-function">() =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'disconnected from server'</span>);
});</code> <button class="copy-button">copy</button></pre>
<p>To connect on the socket <code>/tmp/echo.sock</code>:</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> client = net.<span class="hljs-title function_">createConnection</span>({ <span class="hljs-attr">path</span>: <span class="hljs-string">'/tmp/echo.sock'</span> });</code> <button class="copy-button">copy</button></pre>
<p>Following is an example of a client using the <code>port</code> and <code>onread</code>
option. In this case, the <code>onread</code> option will be only used to call
<code>new net.Socket([options])</code> and the <code>port</code> option will be used to
call <code>socket.connect(options[, connectListener])</code>.</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> net = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>);
net.<span class="hljs-title function_">createConnection</span>({
<span class="hljs-attr">port</span>: <span class="hljs-number">80</span>,
<span class="hljs-attr">onread</span>: {
<span class="hljs-comment">// Reuses a 4KiB Buffer for every read from the socket.</span>
<span class="hljs-attr">buffer</span>: <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">alloc</span>(<span class="hljs-number">4</span> * <span class="hljs-number">1024</span>),
<span class="hljs-attr">callback</span>: <span class="hljs-keyword">function</span>(<span class="hljs-params">nread, buf</span>) {
<span class="hljs-comment">// Received data is available in `buf` from 0 to `nread`.</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(buf.<span class="hljs-title function_">toString</span>(<span class="hljs-string">'utf8'</span>, <span class="hljs-number">0</span>, nread));
},
},
});</code> <button class="copy-button">copy</button></pre>
<h4><code>net.createConnection(path[, connectListener])</code><span><a class="mark" href="#netcreateconnectionpath-connectlistener" id="netcreateconnectionpath-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_createconnection_path_connectlistener"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>path</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Path the socket should connect to. Will be passed to
<a href="#socketconnectpath-connectlistener"><code>socket.connect(path[, connectListener])</code></a>.
See <a href="#identifying-paths-for-ipc-connections">Identifying paths for IPC connections</a>.</li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Common parameter of the
<a href="#netcreateconnection"><code>net.createConnection()</code></a> functions, an "once" listener for the
<code>'connect'</code> event on the initiating socket. Will be passed to
<a href="#socketconnectpath-connectlistener"><code>socket.connect(path[, connectListener])</code></a>.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The newly created socket used to start the connection.</li>
</ul>
<p>Initiates an <a href="#ipc-support">IPC</a> connection.</p>
<p>This function creates a new <a href="#class-netsocket"><code>net.Socket</code></a> with all options set to default,
immediately initiates connection with
<a href="#socketconnectpath-connectlistener"><code>socket.connect(path[, connectListener])</code></a>,
then returns the <code>net.Socket</code> that starts the connection.</p>
<h4><code>net.createConnection(port[, host][, connectListener])</code><span><a class="mark" href="#netcreateconnectionport-host-connectlistener" id="netcreateconnectionport-host-connectlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_createconnection_port_host_connectlistener"></a></h4>
<div class="api_metadata">
<span>Added in: v0.1.90</span>
</div>
<ul>
<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Port the socket should connect to. Will be passed to
<a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a>.</li>
<li><code>host</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host the socket should connect to. Will be passed to
<a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a>.
<strong>Default:</strong> <code>'localhost'</code>.</li>
<li><code>connectListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Common parameter of the
<a href="#netcreateconnection"><code>net.createConnection()</code></a> functions, an "once" listener for the
<code>'connect'</code> event on the initiating socket. Will be passed to
<a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a>.</li>
<li>Returns: <a href="net.html#class-netsocket" class="type"><net.Socket></a> The newly created socket used to start the connection.</li>
</ul>
<p>Initiates a TCP connection.</p>
<p>This function creates a new <a href="#class-netsocket"><code>net.Socket</code></a> with all options set to default,
immediately initiates connection with
<a href="#socketconnectport-host-connectlistener"><code>socket.connect(port[, host][, connectListener])</code></a>,
then returns the <code>net.Socket</code> that starts the connection.</p>
</section><section><h3><code>net.createServer([options][, connectionListener])</code><span><a class="mark" href="#netcreateserveroptions-connectionlistener" id="netcreateserveroptions-connectionlistener">#</a></span><a aria-hidden="true" class="legacy" id="net_net_createserver_options_connectionlistener"></a></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v20.1.0</td>
<td><p>The <code>highWaterMark</code> option is supported now.</p></td></tr>
<tr><td>v17.7.0, v16.15.0</td>
<td><p>The <code>noDelay</code>, <code>keepAlive</code>, and <code>keepAliveInitialDelay</code> options are supported now.</p></td></tr>
<tr><td>v0.5.0</td>
<td><p><span>Added in: v0.5.0</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li>
<p><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></p>
<ul>
<li><code>allowHalfOpen</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to <code>false</code>, then the socket will
automatically end the writable side when the readable side ends.
<strong>Default:</strong> <code>false</code>.</li>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Optionally overrides all <a href="#class-netsocket"><code>net.Socket</code></a>s'
<code>readableHighWaterMark</code> and <code>writableHighWaterMark</code>.
<strong>Default:</strong> See <a href="stream.html#streamgetdefaulthighwatermarkobjectmode"><code>stream.getDefaultHighWaterMark()</code></a>.</li>
<li><code>keepAlive</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to <code>true</code>, it enables keep-alive functionality
on the socket immediately after a new incoming connection is received,
similarly on what is done in <a href="#socketsetkeepaliveenable-initialdelay"><code>socket.setKeepAlive()</code></a>. <strong>Default:</strong>
<code>false</code>.</li>
<li><code>keepAliveInitialDelay</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> If set to a positive number, it sets the
initial delay before the first keepalive probe is sent on an idle socket.
<strong>Default:</strong> <code>0</code>.</li>
<li><code>noDelay</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to <code>true</code>, it disables the use of Nagle's
algorithm immediately after a new incoming connection is received.
<strong>Default:</strong> <code>false</code>.</li>
<li><code>pauseOnConnect</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Indicates whether the socket should be
paused on incoming connections. <strong>Default:</strong> <code>false</code>.</li>
</ul>
</li>
<li>
<p><code>connectionListener</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Automatically set as a listener for the
<a href="#event-connection"><code>'connection'</code></a> event.</p>
</li>
<li>
<p>Returns: <a href="net.html#class-netserver" class="type"><net.Server></a></p>
</li>
</ul>
<p>Creates a new TCP or <a href="#ipc-support">IPC</a> server.</p>
<p>If <code>allowHalfOpen</code> is set to <code>true</code>, when the other end of the socket
signals the end of transmission, the server will only send back the end of
transmission when <a href="#socketenddata-encoding-callback"><code>socket.end()</code></a> is explicitly called. For example, in the
context of TCP, when a FIN packed is received, a FIN packed is sent
back only when <a href="#socketenddata-encoding-callback"><code>socket.end()</code></a> is explicitly called. Until then the
connection is half-closed (non-readable but still writable). See <a href="#event-end"><code>'end'</code></a>
event and <a href="https://tools.ietf.org/html/rfc1122">RFC 1122</a> (section 4.2.2.13) for more information.</p>
<p>If <code>pauseOnConnect</code> is set to <code>true</code>, then the socket associated with each
incoming connection will be paused, and no data will be read from its handle.
This allows connections to be passed between processes without any data being
read by the original process. To begin reading data from a paused socket, call
<a href="#socketresume"><code>socket.resume()</code></a>.</p>
<p>The server can be a TCP server or an <a href="#ipc-support">IPC</a> server, depending on what it
<a href="#serverlisten"><code>listen()</code></a> to.</p>
<p>Here is an example of a TCP echo server which listens for connections
on port 8124:</p>
<pre><code class="language-js"><span class="hljs-keyword">const</span> net = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>);
<span class="hljs-keyword">const</span> server = net.<span class="hljs-title function_">createServer</span>(<span class="hljs-function">(<span class="hljs-params">c</span>) =></span> {
<span class="hljs-comment">// 'connection' listener.</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'client connected'</span>);
c.<span class="hljs-title function_">on</span>(<span class="hljs-string">'end'</span>, <span class="hljs-function">() =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'client disconnected'</span>);
});
c.<span class="hljs-title function_">write</span>(<span class="hljs-string">'hello\r\n'</span>);
c.<span class="hljs-title function_">pipe</span>(c);
});
server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> {
<span class="hljs-keyword">throw</span> err;
});
server.<span class="hljs-title function_">listen</span>(<span class="hljs-number">8124</span>, <span class="hljs-function">() =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'server bound'</span>);
});</code> <button class="copy-button">copy</button></pre>
<p>Test this by using <code>telnet</code>:</p>
<pre><code class="language-bash">telnet localhost 8124</code> <button class="copy-button">copy</button></pre>
<p>To listen on the socket <code>/tmp/echo.sock</code>:</p>
<pre><code class="language-js">server.<span class="hljs-title function_">listen</span>(<span class="hljs-string">'/tmp/echo.sock'</span>, <span class="hljs-function">() =></span> {
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'server bound'</span>);
});</code> <button class="copy-button">copy</button></pre>
<p>Use <code>nc</code> to connect to a Unix domain socket server:</p>
<pre><code class="language-bash">nc -U /tmp/echo.sock</code> <button class="copy-button">copy</button></pre>
</section><section><h3><code>net.getDefaultAutoSelectFamily()</code><span><a class="mark" href="#netgetdefaultautoselectfamily" id="netgetdefaultautoselectfamily">#</a></span><a aria-hidden="true" class="legacy" id="net_net_getdefaultautoselectfamily"></a></h3>
<div class="api_metadata">
<span>Added in: v19.4.0</span>
</div>
<p>Gets the current default value of the <code>autoSelectFamily</code> option of <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.
The initial default value is <code>true</code>, unless the command line option
<code>--no-network-family-autoselection</code> is provided.</p>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> The current default value of the <code>autoSelectFamily</code> option.</li>
</ul>
</section><section><h3><code>net.setDefaultAutoSelectFamily(value)</code><span><a class="mark" href="#netsetdefaultautoselectfamilyvalue" id="netsetdefaultautoselectfamilyvalue">#</a></span><a aria-hidden="true" class="legacy" id="net_net_setdefaultautoselectfamily_value"></a></h3>
<div class="api_metadata">
<span>Added in: v19.4.0</span>
</div>
<p>Sets the default value of the <code>autoSelectFamily</code> option of <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.</p>
<ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> The new default value. The initial default value is <code>false</code>.</li>
</ul>
</section><section><h3><code>net.getDefaultAutoSelectFamilyAttemptTimeout()</code><span><a class="mark" href="#netgetdefaultautoselectfamilyattempttimeout" id="netgetdefaultautoselectfamilyattempttimeout">#</a></span><a aria-hidden="true" class="legacy" id="net_net_getdefaultautoselectfamilyattempttimeout"></a></h3>
<div class="api_metadata">
<span>Added in: v19.8.0</span>
</div>
<p>Gets the current default value of the <code>autoSelectFamilyAttemptTimeout</code> option of <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.
The initial default value is <code>250</code> or the value specified via the command line
option <code>--network-family-autoselection-attempt-timeout</code>.</p>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The current default value of the <code>autoSelectFamilyAttemptTimeout</code> option.</li>
</ul>
</section><section><h3><code>net.setDefaultAutoSelectFamilyAttemptTimeout(value)</code><span><a class="mark" href="#netsetdefaultautoselectfamilyattempttimeoutvalue" id="netsetdefaultautoselectfamilyattempttimeoutvalue">#</a></span><a aria-hidden="true" class="legacy" id="net_net_setdefaultautoselectfamilyattempttimeout_value"></a></h3>
<div class="api_metadata">
<span>Added in: v19.8.0</span>
</div>
<p>Sets the default value of the <code>autoSelectFamilyAttemptTimeout</code> option of <a href="#socketconnectoptions-connectlistener"><code>socket.connect(options)</code></a>.</p>
<ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The new default value, which must be a positive number. If the number is less than <code>10</code>,
the value <code>10</code> is used instead. The initial default value is <code>250</code> or the value specified via the command line
option <code>--network-family-autoselection-attempt-timeout</code>.</li>
</ul>
</section><section><h3><code>net.isIP(input)</code><span><a class="mark" href="#netisipinput" id="netisipinput">#</a></span><a aria-hidden="true" class="legacy" id="net_net_isip_input"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.0</span>
</div>
<ul>
<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns <code>6</code> if <code>input</code> is an IPv6 address. Returns <code>4</code> if <code>input</code> is an IPv4
address in <a href="https://en.wikipedia.org/wiki/Dot-decimal_notation">dot-decimal notation</a> with no leading zeroes. Otherwise, returns
<code>0</code>.</p>
<pre><code class="language-js">net.<span class="hljs-title function_">isIP</span>(<span class="hljs-string">'::1'</span>); <span class="hljs-comment">// returns 6</span>
net.<span class="hljs-title function_">isIP</span>(<span class="hljs-string">'127.0.0.1'</span>); <span class="hljs-comment">// returns 4</span>
net.<span class="hljs-title function_">isIP</span>(<span class="hljs-string">'127.000.000.001'</span>); <span class="hljs-comment">// returns 0</span>
net.<span class="hljs-title function_">isIP</span>(<span class="hljs-string">'127.0.0.1/24'</span>); <span class="hljs-comment">// returns 0</span>
net.<span class="hljs-title function_">isIP</span>(<span class="hljs-string">'fhqwhgads'</span>); <span class="hljs-comment">// returns 0</span></code> <button class="copy-button">copy</button></pre>
</section><section><h3><code>net.isIPv4(input)</code><span><a class="mark" href="#netisipv4input" id="netisipv4input">#</a></span><a aria-hidden="true" class="legacy" id="net_net_isipv4_input"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.0</span>
</div>
<ul>
<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Returns <code>true</code> if <code>input</code> is an IPv4 address in <a href="https://en.wikipedia.org/wiki/Dot-decimal_notation">dot-decimal notation</a> with no
leading zeroes. Otherwise, returns <code>false</code>.</p>
<pre><code class="language-js">net.<span class="hljs-title function_">isIPv4</span>(<span class="hljs-string">'127.0.0.1'</span>); <span class="hljs-comment">// returns true</span>
net.<span class="hljs-title function_">isIPv4</span>(<span class="hljs-string">'127.000.000.001'</span>); <span class="hljs-comment">// returns false</span>
net.<span class="hljs-title function_">isIPv4</span>(<span class="hljs-string">'127.0.0.1/24'</span>); <span class="hljs-comment">// returns false</span>
net.<span class="hljs-title function_">isIPv4</span>(<span class="hljs-string">'fhqwhgads'</span>); <span class="hljs-comment">// returns false</span></code> <button class="copy-button">copy</button></pre>
</section><section><h3><code>net.isIPv6(input)</code><span><a class="mark" href="#netisipv6input" id="netisipv6input">#</a></span><a aria-hidden="true" class="legacy" id="net_net_isipv6_input"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.0</span>
</div>
<ul>
<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>Returns <code>true</code> if <code>input</code> is an IPv6 address. Otherwise, returns <code>false</code>.</p>
<pre><code class="language-js">net.<span class="hljs-title function_">isIPv6</span>(<span class="hljs-string">'::1'</span>); <span class="hljs-comment">// returns true</span>
net.<span class="hljs-title function_">isIPv6</span>(<span class="hljs-string">'fhqwhgads'</span>); <span class="hljs-comment">// returns false</span></code> <button class="copy-button">copy</button></pre></section>
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