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<td >Qt 5.12</td><td ><a href="qtremoteobjects-index.html">Qt Remote Objects</a></td><td >Qt Remote Objects - External QIODevices</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right"><a href="qtremoteobjects-index.html">Qt 5.12.2 Reference Documentation</a></td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#external-qiodevices">External QIODevices</a></li>
<li class="level1"><a href="#external-schemas">External Schemas</a></li>
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<h1 class="title">Qt Remote Objects - External QIODevices</h1>
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<a name="external-qiodevices"></a>
<h2 id="external-qiodevices">External QIODevices</h2>
<p>Qt Remote Objects supports several communications channels out-of-the-box, such as the QTcpServer and QTcpSocket pair. Given the desired QUrl for tcp, or the desired name (for the QLocalServer and QLocalSocket pair), the code needed to listen and connect are boilerplate and handled internally by Qt. Qt Remote Objects supports other types of QIODevice as well, and the <a href="qremoteobjectnode.html">QRemoteObjectNode</a> classes provide additional methods to support cases where custom code is needed.</p>
<p>A contrived example with TCP/IP is shown below. A more realistic example would use an SSL connection, which would require configuration of certificates, etc.</p>
<pre class="cpp">
<span class="comment">// Create the server and listen outside of QtRO</span>
<span class="type">QTcpServer</span> tcpServer;
tcpServer<span class="operator">.</span>listen(<span class="type">QHostAddress</span>(<span class="number">127.0.0.1</span>)<span class="operator">,</span> <span class="number">65213</span>);
<span class="comment">// Create the host node. We don't need a hostUrl unless we want to take</span>
<span class="comment">// advantage of external schemas (see next example).</span>
<span class="type"><a href="qremoteobjecthost.html">QRemoteObjectHost</a></span> srcNode();
<span class="comment">// Make sure any connections are handed to QtRO</span>
<span class="type">QObject</span><span class="operator">::</span>connect(<span class="operator">&</span>tcpServer<span class="operator">,</span> <span class="operator">&</span><span class="type">QTcpServer</span><span class="operator">::</span>newConnection<span class="operator">,</span> <span class="operator">&</span>srcNode<span class="operator">,</span>
<span class="operator">[</span><span class="operator">&</span>srcNode<span class="operator">,</span> <span class="operator">&</span>tcpServer<span class="operator">]</span>() {
srcNode<span class="operator">.</span>addHostSideConnection(tcpServer<span class="operator">.</span>nextPendingConnection());
});
</pre>
<p>The Replica side code needs to manually connect to the Host</p>
<pre class="cpp">
<span class="type"><a href="qremoteobjectnode.html">QRemoteObjectNode</a></span> repNode();
<span class="type">QTcpSocket</span> <span class="operator">*</span>socket <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QTcpSocket</span>(<span class="operator">&</span>repNode);
connect(socket<span class="operator">,</span> <span class="operator">&</span><span class="type">QTcpSocket</span><span class="operator">::</span>connected<span class="operator">,</span> <span class="operator">&</span>repNode<span class="operator">,</span>
<span class="operator">[</span>socket<span class="operator">,</span> <span class="operator">&</span>repNode<span class="operator">]</span>() {
repNode<span class="operator">.</span>addClientSideConnection(socket);
});
socket<span class="operator">-</span><span class="operator">></span>connectToHost(<span class="type">QHostAddress</span>(<span class="number">127.0.0.1</span>)<span class="operator">,</span> <span class="number">65213</span>);
};
</pre>
<a name="external-schemas"></a>
<h2 id="external-schemas">External Schemas</h2>
<p>It is possible to create each side of the QIODevice and call <a href="qremoteobjectnode.html#addClientSideConnection">QRemoteObjectNode::addClientSideConnection</a>(QIODevice *ioDevice) and <a href="qremoteobjecthostbase.html#addHostSideConnection">QRemoteObjectHostBase::addHostSideConnection</a>(QIODevice *ioDevice) as shown above. This is fully supported, but requires the client know how to establish the connection or have a way to discover that information. This is exactly the problem the registry was designed to solve.</p>
<p>Qt Remote Objects also allows "External Schemas" to be used with the registry, which helps with connection setup. On the <a href="qremoteobjecthost.html">QRemoteObjectHost</a> side, the user must set the hostUrl with the desired schema.</p>
<pre class="cpp">
<span class="comment">// Use standard tcp url for the registry</span>
<span class="keyword">const</span> <span class="type">QUrl</span> registryUrl <span class="operator">=</span> <span class="type">QUrl</span>(<span class="type">QStringLiteral</span>(<span class="string">"tcp://127.0.0.1:65212"</span>));
<span class="comment">// Use "exttcp" for the "external" interface</span>
<span class="keyword">const</span> <span class="type">QUrl</span> extUrl <span class="operator">=</span> <span class="type">QUrl</span>(<span class="type">QStringLiteral</span>(<span class="string">"exttcp://127.0.0.1:65213"</span>));
<span class="comment">// Create the server and listen outside of QtRO</span>
<span class="type">QTcpServer</span> tcpServer;
tcpServer<span class="operator">.</span>listen(<span class="type">QHostAddress</span>(extUrl<span class="operator">.</span>host())<span class="operator">,</span> extUrl<span class="operator">.</span>port());
<span class="comment">// We need a registry for everyone to connect to</span>
<span class="type"><a href="qremoteobjectregistryhost.html">QRemoteObjectRegistryHost</a></span> registry(registryUrl);
<span class="comment">// Finally, we create our host node and register "exttcp" as our schema.</span>
<span class="comment">// We need the AllowExternalRegistration parameter to prevent the node from</span>
<span class="comment">// setting a hostUrlInvalid error.</span>
<span class="type"><a href="qremoteobjecthost.html">QRemoteObjectHost</a></span> srcNode(extUrl<span class="operator">,</span> registryUrl<span class="operator">,</span> <span class="type"><a href="qremoteobjecthost.html">QRemoteObjectHost</a></span><span class="operator">::</span>AllowExternalRegistration);
<span class="comment">// From now on, when we call enableRemoting() from this node, the registry</span>
<span class="comment">// will be updated to show the Source object at extUrl.</span>
</pre>
<p>On the <a href="qtremoteobjects-replica.html#replica">Replica</a> side, the <a href="qremoteobjectnode.html">QRemoteObjectNode</a> needs to register a callback to be used when the external schema is detected. The callback must be a <a href="qremoteobjectnode.html#RemoteObjectSchemaHandler-typedef">RemoteObjectSchemaHandler</a>.</p>
<pre class="cpp">
<span class="comment">// Use standard tcp url for the registry</span>
<span class="keyword">const</span> <span class="type">QUrl</span> registryUrl <span class="operator">=</span> <span class="type">QUrl</span>(<span class="type">QStringLiteral</span>(<span class="string">"tcp://127.0.0.1:65212"</span>));
<span class="comment">// This time create the node connected to the registry</span>
<span class="type"><a href="qremoteobjectnode.html">QRemoteObjectNode</a></span> repNode(registryUrl);
<span class="comment">// Create the RemoteObjectSchemaHandler callback</span>
<span class="type"><a href="qremoteobjectnode.html">QRemoteObjectNode</a></span><span class="operator">::</span>RemoteObjectSchemaHandler setupTcp <span class="operator">=</span> <span class="operator">[</span><span class="operator">&</span>repNode<span class="operator">]</span>(<span class="type">QUrl</span> url) {
<span class="type">QTcpSocket</span> <span class="operator">*</span>socket <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QTcpSocket</span>(<span class="operator">&</span>repNode);
connect(socket<span class="operator">,</span> <span class="operator">&</span><span class="type">QTcpSocket</span><span class="operator">::</span>connected<span class="operator">,</span>
<span class="operator">[</span>socket<span class="operator">,</span> <span class="operator">&</span>repNode<span class="operator">]</span>() {
repNode<span class="operator">.</span>addClientSideConnection(socket);
});
connect(socket<span class="operator">,</span> <span class="type">QOverload</span><span class="operator"><</span><span class="type">QAbstractSocket</span><span class="operator">::</span>SocketError<span class="operator">></span><span class="operator">::</span>of(<span class="operator">&</span><span class="type">QSslSocket</span><span class="operator">::</span>error)<span class="operator">,</span>
<span class="operator">[</span>socket<span class="operator">]</span>(<span class="type">QAbstractSocket</span><span class="operator">::</span>SocketError error) {
<span class="keyword">delete</span> socket;
});
socket<span class="operator">-</span><span class="operator">></span>connectToHost(url<span class="operator">.</span>host()<span class="operator">,</span> url<span class="operator">.</span>port());
};
<span class="comment">// Once we call registerExternalSchema, the above method will be called</span>
<span class="comment">// whenever the registry sees an object we are interested in on "exttcp"</span>
repNode<span class="operator">.</span>registerExternalSchema(<span class="type">QStringLiteral</span>(<span class="string">"exttcp"</span>)<span class="operator">,</span> setupTcp);
</pre>
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