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<td >Qt 5.7</td><td ><a href="qtwebsockets-index.html">Qt WebSockets</a></td><td >WebSocket server example</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.7.1 Reference Documentation</td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#description">Description</a></li>
<li class="level1"><a href="#code">Code</a></li>
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<h1 class="title">WebSocket server example</h1>
<span class="subtitle"></span>
<!-- $$$echoserver.html-description -->
<div class="descr"> <a name="details"></a>
<a name="description"></a>
<h2 id="description">Description</h2>
<p>The echoserver example implements a WebSocket server that echoes back everything that is sent to it.</p>
<a name="code"></a>
<h2 id="code">Code</h2>
<p>We start by creating a <a href="qwebsocketserver.html">QWebSocketServer</a> (`new QWebSocketServer()`). After the creation, we listen on all local network interfaces (`<a href="../qtnetwork/qhostaddress.html#SpecialAddress-enum">QHostAddress::Any</a>`) on the specified <i>port</i>.</p>
<pre class="cpp">

  EchoServer<span class="operator">::</span>EchoServer(<span class="type">quint16</span> port<span class="operator">,</span> bool debug<span class="operator">,</span> <span class="type">QObject</span> <span class="operator">*</span>parent) :
      <span class="type">QObject</span>(parent)<span class="operator">,</span>
      m_pWebSocketServer(<span class="keyword">new</span> <span class="type">QWebSocketServer</span>(<span class="type"><a href="../qtcore/qstring.html#QStringLiteral">QStringLiteral</a></span>(<span class="string">&quot;Echo Server&quot;</span>)<span class="operator">,</span>
                                              <span class="type">QWebSocketServer</span><span class="operator">::</span>NonSecureMode<span class="operator">,</span> <span class="keyword">this</span>))<span class="operator">,</span>
      m_clients()<span class="operator">,</span>
      m_debug(debug)
  {
      <span class="keyword">if</span> (m_pWebSocketServer<span class="operator">-</span><span class="operator">&gt;</span>listen(<span class="type">QHostAddress</span><span class="operator">::</span>Any<span class="operator">,</span> port)) {
          <span class="keyword">if</span> (m_debug)
              <a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator">&lt;</span><span class="operator">&lt;</span> <span class="string">&quot;Echoserver listening on port&quot;</span> <span class="operator">&lt;</span><span class="operator">&lt;</span> port;
          connect(m_pWebSocketServer<span class="operator">,</span> <span class="operator">&amp;</span><span class="type">QWebSocketServer</span><span class="operator">::</span>newConnection<span class="operator">,</span>
                  <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&amp;</span>EchoServer<span class="operator">::</span>onNewConnection);
          connect(m_pWebSocketServer<span class="operator">,</span> <span class="operator">&amp;</span><span class="type">QWebSocketServer</span><span class="operator">::</span>closed<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&amp;</span>EchoServer<span class="operator">::</span>closed);
      }
  }

</pre>
<p>If listening is successful, we connect the `newConnection()` signal to the slot `onNewConnection()`. The `newConnection()` signal will be thrown whenever a new WebSocket client is connected to our server.</p>
<pre class="cpp">

  <span class="type">void</span> EchoServer<span class="operator">::</span>onNewConnection()
  {
      <span class="type">QWebSocket</span> <span class="operator">*</span>pSocket <span class="operator">=</span> m_pWebSocketServer<span class="operator">-</span><span class="operator">&gt;</span>nextPendingConnection();

      connect(pSocket<span class="operator">,</span> <span class="operator">&amp;</span><span class="type">QWebSocket</span><span class="operator">::</span>textMessageReceived<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&amp;</span>EchoServer<span class="operator">::</span>processTextMessage);
      connect(pSocket<span class="operator">,</span> <span class="operator">&amp;</span><span class="type">QWebSocket</span><span class="operator">::</span>binaryMessageReceived<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&amp;</span>EchoServer<span class="operator">::</span>processBinaryMessage);
      connect(pSocket<span class="operator">,</span> <span class="operator">&amp;</span><span class="type">QWebSocket</span><span class="operator">::</span>disconnected<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&amp;</span>EchoServer<span class="operator">::</span>socketDisconnected);

      m_clients <span class="operator">&lt;</span><span class="operator">&lt;</span> pSocket;
  }

</pre>
<p>When a new connection is received, the client <a href="qwebsocket.html">QWebSocket</a> is retrieved (`nextPendingConnection()`), and the signals we are interested in are connected to our slots (`textMessageReceived()`, `binaryMessageReceived()` and `disconnected()`). The client socket is remembered in a list, in case we would like to use it later (in this example, nothing is done with it).</p>
<pre class="cpp">

  <span class="type">void</span> EchoServer<span class="operator">::</span>processTextMessage(<span class="type">QString</span> message)
  {
      <span class="type">QWebSocket</span> <span class="operator">*</span>pClient <span class="operator">=</span> qobject_cast<span class="operator">&lt;</span><span class="type">QWebSocket</span> <span class="operator">*</span><span class="operator">&gt;</span>(sender());
      <span class="keyword">if</span> (m_debug)
          <a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator">&lt;</span><span class="operator">&lt;</span> <span class="string">&quot;Message received:&quot;</span> <span class="operator">&lt;</span><span class="operator">&lt;</span> message;
      <span class="keyword">if</span> (pClient) {
          pClient<span class="operator">-</span><span class="operator">&gt;</span>sendTextMessage(message);
      }
  }

</pre>
<p>Whenever `processTextMessage()` is triggered, we retrieve the sender, and if valid, send back the original message (`sendTextMessage()`). The same is done with binary messages.</p>
<pre class="cpp">

  <span class="type">void</span> EchoServer<span class="operator">::</span>processBinaryMessage(<span class="type">QByteArray</span> message)
  {
      <span class="type">QWebSocket</span> <span class="operator">*</span>pClient <span class="operator">=</span> qobject_cast<span class="operator">&lt;</span><span class="type">QWebSocket</span> <span class="operator">*</span><span class="operator">&gt;</span>(sender());
      <span class="keyword">if</span> (m_debug)
          <a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator">&lt;</span><span class="operator">&lt;</span> <span class="string">&quot;Binary Message received:&quot;</span> <span class="operator">&lt;</span><span class="operator">&lt;</span> message;
      <span class="keyword">if</span> (pClient) {
          pClient<span class="operator">-</span><span class="operator">&gt;</span>sendBinaryMessage(message);
      }
  }

</pre>
<p>The only difference is that the message now is a <a href="../qtcore/qbytearray.html">QByteArray</a> instead of a <a href="../qtcore/qstring.html">QString</a>.</p>
<pre class="cpp">

  <span class="type">void</span> EchoServer<span class="operator">::</span>socketDisconnected()
  {
      <span class="type">QWebSocket</span> <span class="operator">*</span>pClient <span class="operator">=</span> qobject_cast<span class="operator">&lt;</span><span class="type">QWebSocket</span> <span class="operator">*</span><span class="operator">&gt;</span>(sender());
      <span class="keyword">if</span> (m_debug)
          <a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator">&lt;</span><span class="operator">&lt;</span> <span class="string">&quot;socketDisconnected:&quot;</span> <span class="operator">&lt;</span><span class="operator">&lt;</span> pClient;
      <span class="keyword">if</span> (pClient) {
          m_clients<span class="operator">.</span>removeAll(pClient);
          pClient<span class="operator">-</span><span class="operator">&gt;</span>deleteLater();
      }
  }

</pre>
<p>Whenever a socket is disconnected, we remove it from the clients list and delete the socket. Note: it is best to use `deleteLater()` to delete the socket.</p>
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