WebSocket server example
Description
The echoserver example implements a WebSocket server that echoes back everything that is sent to it.
Code
We start by creating a QWebSocketServer (`new QWebSocketServer()`). After the creation, we listen on all local network interfaces (`QHostAddress::Any`) on the specified port.
EchoServer::EchoServer(quint16 port, bool debug, QObject *parent) : QObject(parent), m_pWebSocketServer(new QWebSocketServer(QStringLiteral("Echo Server"), QWebSocketServer::NonSecureMode, this)), m_debug(debug) { if (m_pWebSocketServer->listen(QHostAddress::Any, port)) { if (m_debug) qDebug() << "Echoserver listening on port" << port; connect(m_pWebSocketServer, &QWebSocketServer::newConnection, this, &EchoServer::onNewConnection); connect(m_pWebSocketServer, &QWebSocketServer::closed, this, &EchoServer::closed); } }
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.
void EchoServer::onNewConnection() { QWebSocket *pSocket = m_pWebSocketServer->nextPendingConnection(); connect(pSocket, &QWebSocket::textMessageReceived, this, &EchoServer::processTextMessage); connect(pSocket, &QWebSocket::binaryMessageReceived, this, &EchoServer::processBinaryMessage); connect(pSocket, &QWebSocket::disconnected, this, &EchoServer::socketDisconnected); m_clients << pSocket; }
When a new connection is received, the client QWebSocket 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).
void EchoServer::processTextMessage(QString message) { QWebSocket *pClient = qobject_cast<QWebSocket *>(sender()); if (m_debug) qDebug() << "Message received:" << message; if (pClient) { pClient->sendTextMessage(message); } }
Whenever `processTextMessage()` is triggered, we retrieve the sender, and if valid, send back the original message (`sendTextMessage()`). The same is done with binary messages.
void EchoServer::processBinaryMessage(QByteArray message) { QWebSocket *pClient = qobject_cast<QWebSocket *>(sender()); if (m_debug) qDebug() << "Binary Message received:" << message; if (pClient) { pClient->sendBinaryMessage(message); } }
The only difference is that the message now is a QByteArray instead of a QString.
void EchoServer::socketDisconnected() { QWebSocket *pClient = qobject_cast<QWebSocket *>(sender()); if (m_debug) qDebug() << "socketDisconnected:" << pClient; if (pClient) { m_clients.removeAll(pClient); pClient->deleteLater(); } }
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.
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Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-5.9/echoserver.html