---
title: WebSocket.protocol
slug: Web/API/WebSocket/protocol
translation_of: Web/API/WebSocket/protocol
---
<p>{{APIRef("Web Sockets API")}}</p>

<p><strong><code>WebSocket.protocol</code></strong> 是个只读属性，用于返回服务器端选中的子协议的名字；这是一个在创建{{domxref("WebSocket")}} 对象时，在参数{{domxref("<code>protocols</code>")}}中指定的字符串，当没有已建立的链接时为空串。</p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox notranslate">var protocol = <em>aWebSocket</em>.protocol;</pre>

<h2 id="返回值">返回值</h2>

<p><a href="https://developer.mozilla.org/en-US/docs/Web/API/DOMString" title="DOMString is a UTF-16 String. As JavaScript already uses such strings, DOMString is mapped directly to a String."><code>DOMString</code></a>.</p>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('HTML WHATWG', '#dom-websocket-protocol', 'WebSocket: protocol')}}</td>
   <td>{{Spec2('HTML WHATWG')}}</td>
   <td>Initial definition</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>



<p>{{Compat("api.WebSocket.protocol")}}</p>