Web Socket

A lightweight RFC 6455 (Web Socket) implementation for Qt5 & Qt6 by Calin Culianu calin.culianu@gmail.com

Key highlights:

• Supports both ws:// and wss:// Web Sockets.
• Support both client-side and server-side mode of operation.
• Easy to integrate: just copy WebSocket.h and WebSocket.cpp into your project
• Easy to use with existing codebases:
  • Unlike the QWebSocket module from Qt, this code's main class, WebSocket::Wrapper inherits from QTcpSocket and thus can easily be integrated into existing code.
  • In other words, the key paradigm offered is basically a generic wrapper for a regular QTcpSocket that itself inherits from QTcpSocket.
• Asynchronous mode of operation (requires an event loop in the thread the WebSocket::Wrapper lives in).
• Requires C++17.

How to use in your project

1. Copy WebSocket.h and WebSocket.cpp into your project.
2. Enjoy! (The license here is MIT so you can use this in any project, commercial or open source).

Quick Example (Client Side)

Note that this example is to illustrate how to use WebSocket::Wrapper, and some key things have been omitted (such as handling all possible failures and/or cleaning up resources on all possible failure modes, etc).

#include "WebSocket.h"

// ... and somewhere in your code:

// create the to-be-wrapped socket (this is the real socket)
QTcpSocket *sock = new QTcpSocket(this);

connect(sock, &QTcpSocket::connected, this, [this, sock]{
    // create the socket wrapper
    auto websock = new WebSocket::Wrapper(sock, this);
    // 'sock' is now a child of 'websock' ('websock' wraps 'sock').
    // (do not use 'sock' directly anymore, instead use 'websock').

    // We will start the handshake process below:

    // register the success signal (emitted if the handshake succeeds)
    connect(websock, &WebSocket::Wrapper::handshakeSuccess, this, [this, websock]{
       // save the active socket here and use it...
       // At this point the conneciton is "speaking" the web socket protocol
       // You can call websock->write(), to send.
       // Use the `messagesReady()` or `readyRead()` signals to receive framed
       // messages.
       this->connectedSock = websock;
       // use it.... emit a signal here, etc...
    });
    // we need to also handle failures
    connect(websock, &WebSocket::Wrapper::handshakeFailed, this, [this, websock](const QString & reason){
        // handle failure, delete the socket, etc
        qWarning() << "WebSocket handshake failed:" << reason;
        // below will also delete child wrapped socket...
        websock->deleteLater();
    });
    auto res = websock->startClientHandshake("/", "somehost.com");
    // ^ some time later either handshakeSuccess() or handshakeFailed() will be emitted by 'websock'

    if (!res)
        // this should not normally happen, but it pays to be careful
        websock->deleteLater();
});

sock->connectToHost(someHost, somePort);

// be sure to add code to handle connection failures here too (omitted from this example).

Quick Example (Server Side)

Note that this example is to illustrate how to use WebSocket::Wrapper, and some key things have been omitted (such as handling all possible failures and/or cleaning up resources on all possible failure modes, etc).

#include <QTcpServer>
#include "WebSocket.h"

// You must inherit QTcpServer and override incomingConnection(qintptr)
void MyTcpServer::incomingConnection(qintptr socketDescriptor)
{
    QTcpSocket *socket = new QTcpSocket(this);
    socket->setSocketDescriptor(socketDescriptor);
    // the below wrapper `ws` becomes parent of the socket,
    // and `this` is now parent of the wrapper.
    auto ws = new WebSocket::Wrapper(socket, this);

    // do not access `socket` below this line, use `ws` instead.

    connect(ws, &WebSocket::Wrapper::handshakeSuccess, this, [this, ws] {
        addPendingConnection(ws);
        // We must emit newConnection() here because we went asynch and are doing this 'some time later', and the calling code emitted a spurous newConnection() on our behalf previously.. and this is the *real* newConnection()
        emit newConnection();
    });
    // handle handshake failure as well
    connect(ws, &WebSocket::Wrapper::handshakeFailed, this, [ws](const QString &reason) {
        qWarning() << "WebSocket handshake failed:" <<  reason;
        ws->deleteLater();
    });

    auto res = ws->startServerHandshake();
    // ^ some time later either handshakeSuccess() or handshakeFailed() will be emitted by 'ws'

    if (!res)
        // this should not normally happen
        ws->deleteLater();
}

More examples

Please see the examples/ subdiectory for the sample "TestEchoClientServer" stand-alone CLI program for testing, as well as a user-contributed sample application. More examples coming soon!

License

MIT

Donations

Yes please! Bitcoin or Bitcoin Cash to this address please: 1Ca1inCimwRhhcpFX84TPRrPQSryTgKW6N