---
title: WebSocket
slug: Web/API/WebSocket
translation_of: Web/API/WebSocket
---
<div>{{APIRef("Web Sockets API")}}{{SeeCompatTable}}</div>

<p>Об'єкт <code>WebSocket надає </code>API (інтерфейс) для створення і керування  <a href="/en-US/docs/Web/API/WebSockets_API">WebSocket</a>-з'єднаннями з сервером connection to a server, а також для надсилання і отримання повідомлень з даними.</p>

<p>Конструктор WebSocket приймає один обов'язковий і один опціональний параметр:</p>

<pre class="syntaxbox">new WebSocket(
  in DOMString url,
  in optional DOMString protocols
);
</pre>

<dl>
 <dt><code>url</code></dt>
 <dd>Це адреса URL, до якої треба підключитись. Тобто адреса, з якої буде відповідати WebSocket на сервері.</dd>
 <dt><code>protocols</code> {{optional_inline}}</dt>
 <dd>Це один протокол або масив протоколів. Протокол - це текст. Ці протоколи потрібні, щоб вказати під-протоколи, щоб один сервер міг виконувати декілька під-протоколів WebSocket (на приклад, вам потрібен сервер, який здатний працювати з різними типами взаємодій залежно від протоколу). Якщо ви не вкажете протокол, то WebSocket буде вважати, що отримав пустий рядок.</dd>
</dl>

<p>Конструктор може повертати помилки. На прикладі нижче помилка про "порт, до якого була спроба підключитися, був заблокований":</p>

<dl>
 <dt><code>SECURITY_ERR</code></dt>
 <dd>The port to which the connection is being attempted is being blocked.</dd>
</dl>

<h2 id="Method_overview">Method overview</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <td><code>void <a href="#close()">close</a>(in optional unsigned long code, in optional DOMString reason);</code></td>
  </tr>
  <tr>
   <td><code>void <a href="#send()">send</a>(in DOMString data);</code></td>
  </tr>
 </tbody>
</table>

<h2 id="Attributes">Attributes</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <td class="header">Attribute</td>
   <td class="header">Type</td>
   <td class="header">Description</td>
  </tr>
  <tr>
   <td><code>binaryType</code></td>
   <td>{{DOMXref("DOMString")}}</td>
   <td>A string indicating the type of binary data being transmitted by the connection. This should be either "blob" if DOM {{domxref("Blob")}} objects are being used or "arraybuffer" if {{jsxref("ArrayBuffer")}} objects are being used.</td>
  </tr>
  <tr>
   <td><code>bufferedAmount</code></td>
   <td><code>unsigned long</code></td>
   <td>The number of bytes of data that have been queued using calls to {{manch("send")}} but not yet transmitted to the network. This value resets to zero once all queued data has been sent. This value does not reset to zero when the connection is closed; if you keep calling {{manch("send")}}, this will continue to climb. <strong>Read only</strong></td>
  </tr>
  <tr>
   <td><code>extensions</code></td>
   <td>{{DOMXref("DOMString")}}</td>
   <td>The extensions selected by the server. This is currently only the empty string or a list of extensions as negotiated by the connection.</td>
  </tr>
  <tr>
   <td><code>onclose</code></td>
   <td>{{domxref("EventListener")}}</td>
   <td>An event listener to be called when the WebSocket connection's <code>readyState</code> changes to <code>CLOSED</code>. The listener receives a <a href="/en-US/docs/Web/API/CloseEvent"><code>CloseEvent</code></a> named "close".</td>
  </tr>
  <tr>
   <td><code>onerror</code></td>
   <td>{{domxref("EventListener")}}</td>
   <td>An event listener to be called when an error occurs. This is a simple event named "error".</td>
  </tr>
  <tr>
   <td><code>onmessage</code></td>
   <td>{{domxref("EventListener")}}</td>
   <td>An event listener to be called when a message is received from the server. The listener receives a <a href="/en-US/docs/Web/API/MessageEvent"><code>MessageEvent</code></a> named "message".</td>
  </tr>
  <tr>
   <td><code>onopen</code></td>
   <td>{{domxref("EventListener")}}</td>
   <td>An event listener to be called when the WebSocket connection's <code>readyState</code> changes to <code>OPEN</code>; this indicates that the connection is ready to send and receive data. The event is a simple one with the name "open".</td>
  </tr>
  <tr>
   <td><code>protocol</code></td>
   <td>{{DOMXref("DOMString")}}</td>
   <td>A string indicating the name of the sub-protocol the server selected; this will be one of the strings specified in the <code>protocols</code> parameter when creating the WebSocket object.</td>
  </tr>
  <tr>
   <td><code>readyState</code></td>
   <td><code>unsigned short</code></td>
   <td>The current state of the connection; this is one of the {{anch("Ready state constants")}}. <strong>Read only.</strong></td>
  </tr>
  <tr>
   <td><code>url</code></td>
   <td>{{DOMXref("DOMString")}}</td>
   <td>The URL as resolved by the constructor. This is always an absolute URL. <strong>Read only.</strong></td>
  </tr>
 </tbody>
</table>

<h2 id="Constants">Constants</h2>

<h3 id="Ready_state_constants">Ready state constants</h3>

<p>These constants are used by the <code>readyState</code> attribute to describe the state of the WebSocket connection.</p>

<table class="standard-table">
 <tbody>
  <tr>
   <td class="header">Constant</td>
   <td class="header">Value</td>
   <td class="header">Description</td>
  </tr>
  <tr>
   <td><code>CONNECTING</code></td>
   <td><code>0</code></td>
   <td>The connection is not yet open.</td>
  </tr>
  <tr>
   <td><code>OPEN</code></td>
   <td><code>1</code></td>
   <td>The connection is open and ready to communicate.</td>
  </tr>
  <tr>
   <td><code>CLOSING</code></td>
   <td><code>2</code></td>
   <td>The connection is in the process of closing.</td>
  </tr>
  <tr>
   <td><code>CLOSED</code></td>
   <td><code>3</code></td>
   <td>The connection is closed or couldn't be opened.</td>
  </tr>
 </tbody>
</table>

<h2 id="Methods">Methods</h2>

<h3 id="close()">close()</h3>

<p>Closes the WebSocket connection or connection attempt, if any. If the connection is already <code>CLOSED</code>, this method does nothing.</p>

<pre class="syntaxbox">void close(
  in optional unsigned short code,
  in optional DOMString reason
);
</pre>

<h4 id="Parameters">Parameters</h4>

<dl>
 <dt><code>code</code> {{optional_inline}}</dt>
 <dd>A numeric value indicating the status code explaining why the connection is being closed. If this parameter is not specified, a default value of 1000 (indicating a normal "transaction complete" closure) is assumed. See the <a href="/en-US/docs/Web/API/CloseEvent#Status_codes">list of status codes</a> on the <a href="/en-US/docs/Web/API/CloseEvent"><code>CloseEvent</code></a> page for permitted values.</dd>
 <dt><code>reason</code> {{optional_inline}}</dt>
 <dd>A human-readable string explaining why the connection is closing. This string must be no longer than 123 bytes of UTF-8 text (<strong>not</strong> characters).</dd>
</dl>

<h4 id="Exceptions_thrown">Exceptions thrown</h4>

<dl>
 <dt><code>INVALID_ACCESS_ERR</code></dt>
 <dd>An invalid <code>code</code> was specified.</dd>
 <dt><code>SYNTAX_ERR</code></dt>
 <dd>The <code>reason</code> string is too long or contains unpaired surrogates.</dd>
</dl>

<div class="note">
<p><strong>Note:</strong> In Gecko, this method didn't support any parameters prior to Gecko 8.0 {{geckoRelease("8.0")}}.</p>
</div>

<h3 id="send()">send()</h3>

<p>Transmits data to the server over the WebSocket connection.</p>

<pre class="syntaxbox">void send(
  in DOMString data
);

void send(
  in ArrayBuffer data
);

void send(
  in Blob data
);
</pre>

<h4 id="Parameters_2">Parameters</h4>

<dl>
 <dt><code>data</code></dt>
 <dd>A text string to send to the server.</dd>
</dl>

<h4 id="Exceptions_thrown_2">Exceptions thrown</h4>

<dl>
 <dt><code>INVALID_STATE_ERR</code></dt>
 <dd>The connection is not currently <code>OPEN</code>.</dd>
 <dt><code>SYNTAX_ERR</code></dt>
 <dd>The data is a string that has unpaired surrogates.</dd>
</dl>

<div class="note">
<p><strong>Note:</strong> Gecko's implementation of the <code>send()</code> method differs somewhat from the specification in {{Gecko("6.0")}}; Gecko returns a <code>boolean</code> indicating whether or not the connection is still open (and, by extension, that the data was successfully queued or transmitted); this is corrected in {{Gecko("8.0")}}.</p>

<p>As of {{Gecko("11.0")}}, support for {{jsxref("ArrayBuffer")}} is implemented but not {{domxref("Blob")}} data types.</p>
</div>

<h2 id="Example">Example</h2>

<pre class="brush: js">// Create WebSocket connection.
const socket = new WebSocket('ws://localhost:8080');

// Connection opened
socket.addEventListener('open', function (event) {
    socket.send('Hello Server!');
});

// Listen for messages
socket.addEventListener('message', function (event) {
    console.log('Message from server', event.data);
});</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th>Specification</th>
   <th>Status</th>
   <th>Comment</th>
  </tr>
  <tr>
   <td>{{SpecName("Websockets", "#the-websocket-interface", "WebSocket")}}</td>
   <td>{{Spec2("Websockets")}}</td>
   <td>Initial definition</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Edge</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop("2.0")}}<sup>[1]</sup></td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
  <tr>
   <td>Sub-protocol support</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatGeckoDesktop("6.0")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Edge</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoMobile("7.0")}}<sup>[1]</sup></td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
  <tr>
   <td>Sub-protocol support</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatGeckoMobile("7.0")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<p>[1] Starting in Gecko 6.0 {{geckoRelease("6.0")}}, the constructor is prefixed; you will need to use <code>MozWebSocket()</code>: <code>var mySocket = new MozWebSocket("http://www.example.com/socketserver");</code></p>

<p>The <code>extensions</code> attribute was not supported in Gecko until Gecko 8.0.</p>

<p>Prior to Gecko 11.0 {{geckoRelease("11.0")}}, outbound messages sent using the <a href="#send()">send()</a> method were limited to 16 MB. They can now be up to 2 GB in size.</p>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="/en-US/docs/Web/API/WebSockets_API/Writing_WebSocket_client_applications">Writing WebSocket client applications</a></li>
</ul>