<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- fortuneserver.qdoc --> <title>Fortune Server Example | Qt Network 5.12.6</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.12</td><td ><a href="qtnetwork-index.html">Qt Network</a></td><td ><a href="examples-network.html">Network Examples</a></td><td >Fortune Server Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtnetwork-index.html">Qt 5.12.6 Reference Documentation</a></td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"><div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Fortune Server Example</h1> <span class="subtitle"></span> <!-- $$$fortuneserver-brief --> <p>Demonstrates how to create a server for a network service.</p> <!-- @@@fortuneserver --> <!-- $$$fortuneserver-description --> <div class="descr"> <a name="details"></a> <p>This example is intended to be run alongside the <a href="qtnetwork-fortuneclient-example.html">Fortune Client</a> example or the <a href="qtnetwork-blockingfortuneclient-example.html">Blocking Fortune Client Example</a>.</p> <p class="centerAlign"><img src="images/fortuneserver-example.png" alt="Screenshot of the Fortune Server example" /></p><p>It uses <a href="qtcpserver.html">QTcpServer</a> to accept incoming TCP connections, and a simple <a href="../qtcore/qdatastream.html">QDataStream</a> based data transfer protocol to write a fortune to the connecting client (from the <a href="qtnetwork-fortuneclient-example.html">Fortune Client</a> example), before closing the connection.</p> <pre class="cpp"> <span class="keyword">class</span> Server : <span class="keyword">public</span> <span class="type">QDialog</span> { Q_OBJECT <span class="keyword">public</span>: <span class="keyword">explicit</span> Server(<span class="type">QWidget</span> <span class="operator">*</span>parent <span class="operator">=</span> nullptr); <span class="keyword">private</span> <span class="keyword">slots</span>: <span class="type">void</span> sessionOpened(); <span class="type">void</span> sendFortune(); <span class="keyword">private</span>: <span class="type">QLabel</span> <span class="operator">*</span>statusLabel <span class="operator">=</span> nullptr; <span class="type"><a href="qtcpserver.html">QTcpServer</a></span> <span class="operator">*</span>tcpServer <span class="operator">=</span> nullptr; <span class="type"><a href="../qtcore/qvector.html">QVector</a></span><span class="operator"><</span><span class="type"><a href="../qtcore/qstring.html">QString</a></span><span class="operator">></span> fortunes; <span class="type"><a href="qnetworksession.html">QNetworkSession</a></span> <span class="operator">*</span>networkSession <span class="operator">=</span> nullptr; }; </pre> <p>The server is implemented using a simple class with only one slot, for handling incoming connections.</p> <pre class="cpp"> tcpServer <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qtcpserver.html">QTcpServer</a></span>(<span class="keyword">this</span>); <span class="keyword">if</span> (<span class="operator">!</span>tcpServer<span class="operator">-</span><span class="operator">></span>listen()) { <span class="type">QMessageBox</span><span class="operator">::</span>critical(<span class="keyword">this</span><span class="operator">,</span> tr(<span class="string">"Fortune Server"</span>)<span class="operator">,</span> tr(<span class="string">"Unable to start the server: %1."</span>) <span class="operator">.</span>arg(tcpServer<span class="operator">-</span><span class="operator">></span>errorString())); close(); <span class="keyword">return</span>; } <span class="type"><a href="../qtcore/qstring.html">QString</a></span> ipAddress; <span class="type"><a href="../qtcore/qlist.html">QList</a></span><span class="operator"><</span><span class="type"><a href="qhostaddress.html">QHostAddress</a></span><span class="operator">></span> ipAddressesList <span class="operator">=</span> <span class="type"><a href="qnetworkinterface.html">QNetworkInterface</a></span><span class="operator">::</span>allAddresses(); <span class="comment">// use the first non-localhost IPv4 address</span> <span class="keyword">for</span> (<span class="type">int</span> i <span class="operator">=</span> <span class="number">0</span>; i <span class="operator"><</span> ipAddressesList<span class="operator">.</span>size(); <span class="operator">+</span><span class="operator">+</span>i) { <span class="keyword">if</span> (ipAddressesList<span class="operator">.</span>at(i) <span class="operator">!</span><span class="operator">=</span> <span class="type"><a href="qhostaddress.html">QHostAddress</a></span><span class="operator">::</span>LocalHost <span class="operator">&</span><span class="operator">&</span> ipAddressesList<span class="operator">.</span>at(i)<span class="operator">.</span>toIPv4Address()) { ipAddress <span class="operator">=</span> ipAddressesList<span class="operator">.</span>at(i)<span class="operator">.</span>toString(); <span class="keyword">break</span>; } } <span class="comment">// if we did not find one, use IPv4 localhost</span> <span class="keyword">if</span> (ipAddress<span class="operator">.</span>isEmpty()) ipAddress <span class="operator">=</span> <span class="type"><a href="qhostaddress.html">QHostAddress</a></span>(<span class="type"><a href="qhostaddress.html">QHostAddress</a></span><span class="operator">::</span>LocalHost)<span class="operator">.</span>toString(); statusLabel<span class="operator">-</span><span class="operator">></span>setText(tr(<span class="string">"The server is running on\n\nIP: %1\nport: %2\n\n"</span> <span class="string">"Run the Fortune Client example now."</span>) <span class="operator">.</span>arg(ipAddress)<span class="operator">.</span>arg(tcpServer<span class="operator">-</span><span class="operator">></span>serverPort())); </pre> <p>In its constructor, our Server object calls <a href="qtcpserver.html#listen">QTcpServer::listen</a>() to set up a <a href="qtcpserver.html">QTcpServer</a> to listen on all addresses, on an arbitrary port. In then displays the port <a href="qtcpserver.html">QTcpServer</a> picked in a label, so that user knows which port the fortune client should connect to.</p> <pre class="cpp"> fortunes <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"You've been leading a dog's life. Stay off the furniture."</span>) <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"You've got to think about tomorrow."</span>) <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"You will be surprised by a loud noise."</span>) <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"You will feel hungry again in another hour."</span>) <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"You might have mail."</span>) <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"You cannot kill time without injuring eternity."</span>) <span class="operator"><</span><span class="operator"><</span> tr(<span class="string">"Computers are not intelligent. They only think they are."</span>); </pre> <p>Our server generates a list of random fortunes that it can send to connecting clients.</p> <pre class="cpp"> connect(tcpServer<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="qtcpserver.html">QTcpServer</a></span><span class="operator">::</span>newConnection<span class="operator">,</span> <span class="keyword">this</span><span class="operator">,</span> <span class="operator">&</span>Server<span class="operator">::</span>sendFortune); </pre> <p>When a client connects to our server, <a href="qtcpserver.html">QTcpServer</a> will emit <a href="qtcpserver.html#newConnection">QTcpServer::newConnection</a>(). In turn, this will invoke our sendFortune() slot:</p> <pre class="cpp"> <span class="type">void</span> Server<span class="operator">::</span>sendFortune() { <span class="type"><a href="../qtcore/qbytearray.html">QByteArray</a></span> block; <span class="type"><a href="../qtcore/qdatastream.html">QDataStream</a></span> out(<span class="operator">&</span>block<span class="operator">,</span> <span class="type"><a href="../qtcore/qiodevice.html">QIODevice</a></span><span class="operator">::</span>WriteOnly); out<span class="operator">.</span>setVersion(<span class="type"><a href="../qtcore/qdatastream.html">QDataStream</a></span><span class="operator">::</span>Qt_5_10); out <span class="operator"><</span><span class="operator"><</span> fortunes<span class="operator">[</span><span class="type"><a href="../qtcore/qrandomgenerator.html">QRandomGenerator</a></span><span class="operator">::</span>global()<span class="operator">-</span><span class="operator">></span>bounded(fortunes<span class="operator">.</span>size())<span class="operator">]</span>; </pre> <p>The purpose of this slot is to select a random line from our list of fortunes, encode it into a <a href="../qtcore/qbytearray.html">QByteArray</a> using <a href="../qtcore/qdatastream.html">QDataStream</a>, and then write it to the connecting socket. This is a common way to transfer binary data using <a href="qtcpsocket.html">QTcpSocket</a>. First we create a <a href="../qtcore/qbytearray.html">QByteArray</a> and a <a href="../qtcore/qdatastream.html">QDataStream</a> object, passing the bytearray to <a href="../qtcore/qdatastream.html">QDataStream</a>'s constructor. We then explicitly set the protocol version of <a href="../qtcore/qdatastream.html">QDataStream</a> to <a href="../qtcore/qdatastream.html#Version-enum">QDataStream::Qt_4_0</a> to ensure that we can communicate with clients from future versions of Qt (see <a href="../qtcore/qdatastream.html#setVersion">QDataStream::setVersion</a>()). We continue by streaming in a random fortune.</p> <pre class="cpp"> <span class="type"><a href="qtcpsocket.html">QTcpSocket</a></span> <span class="operator">*</span>clientConnection <span class="operator">=</span> tcpServer<span class="operator">-</span><span class="operator">></span>nextPendingConnection(); connect(clientConnection<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="qabstractsocket.html">QAbstractSocket</a></span><span class="operator">::</span>disconnected<span class="operator">,</span> clientConnection<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="../qtcore/qobject.html">QObject</a></span><span class="operator">::</span>deleteLater); </pre> <p>We then call <a href="qtcpserver.html#nextPendingConnection">QTcpServer::nextPendingConnection</a>(), which returns the <a href="qtcpsocket.html">QTcpSocket</a> representing the server side of the connection. By connecting <a href="qabstractsocket.html#disconnected">QTcpSocket::disconnected</a>() to <a href="../qtcore/qobject.html#deleteLater">QObject::deleteLater</a>(), we ensure that the socket will be deleted after disconnecting.</p> <pre class="cpp"> clientConnection<span class="operator">-</span><span class="operator">></span>write(block); clientConnection<span class="operator">-</span><span class="operator">></span>disconnectFromHost(); } </pre> <p>The encoded fortune is written using <a href="../qtcore/qiodevice.html#write-2">QTcpSocket::write</a>(), and we finally call <a href="qabstractsocket.html#disconnectFromHost">QTcpSocket::disconnectFromHost</a>(), which will close the connection after <a href="qtcpsocket.html">QTcpSocket</a> has finished writing the fortune to the network. Because <a href="qtcpsocket.html">QTcpSocket</a> works asynchronously, the data will be written after this function returns, and control goes back to Qt's event loop. The socket will then close, which in turn will cause <a href="../qtcore/qobject.html#deleteLater">QObject::deleteLater</a>() to delete it.</p> <p>Files:</p> <ul> <li><a href="qtnetwork-fortuneserver-fortuneserver-pro.html">fortuneserver/fortuneserver.pro</a></li> <li><a href="qtnetwork-fortuneserver-main-cpp.html">fortuneserver/main.cpp</a></li> <li><a href="qtnetwork-fortuneserver-server-cpp.html">fortuneserver/server.cpp</a></li> <li><a href="qtnetwork-fortuneserver-server-h.html">fortuneserver/server.h</a></li> </ul> </div> <p><b>See also </b><a href="qtnetwork-fortuneclient-example.html">Fortune Client Example</a> and <a href="qtnetwork-threadedfortuneserver-example.html">Threaded Fortune Server Example</a>.</p> <!-- @@@fortuneserver --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2019 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br/> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br/> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>