QHttpServer and WebSockets

[Mr.Betatester]

I try to use the QHttpServer and setup a WebSocket connection for realtime updates (because SSE ist not implemented at the QHttpServer at the moment).

When I start the connection the WebSocket will be closed directly after the newWebSocketConnectionSlot was processed.

Server startup:

    m_httpServer.route(m_frontendDir + "/app.js", [this]() { return QHttpServerResponse(m_frontendJS); });
    m_httpServer.route("/", [this](const QHttpServerRequest& request) { return getPage(request); });
    m_httpServer.route("/data/", [this](const QString& table, const QHttpServerRequest& request) { return getData(request, table); });
    connect(&m_httpServer, SIGNAL(newWebSocketConnection()), this, SLOT(newWebSocketConnection()));

WebSocket handling:

void AGVWebServer::newWebSocketConnection()
{
    if (m_httpServer.hasPendingWebSocketConnections() == true) {
        std::unique_ptr<QWebSocket> up_socket = m_httpServer.nextPendingWebSocketConnection();
        m_clients.push_back(std::move(up_socket));

        QWebSocket* socket = m_clients[m_clients.size() - 1].get();

        connect(socket, &QWebSocket::textMessageReceived, this, &AGVWebServer::processTextMessage);
        connect(socket, &QWebSocket::disconnected, this, &AGVWebServer::socketDisconnected);

    }
}


void AGVWebServer::processTextMessage(QString message)
{
    QWebSocket *pClient = qobject_cast<QWebSocket *>(sender());

    if (pClient) {
        pClient->sendTextMessage(message);
    }
}


void AGVWebServer::socketDisconnected()
{
    QWebSocket *pClient = qobject_cast<QWebSocket *>(sender());

    if (pClient) {
        //TODO m_clients.removeAll(pClient);
        pClient->deleteLater();
    }
}

My current workaround is to start a feature task that will never end to keep the connection open:

    m_httpServer.route("/notification", [this]() {
        return QtConcurrent::run([this] () {
            QEventLoop loop;
            connect(this, &AGVWebServer::stopWebSockets, &loop, &QEventLoop::quit);
            loop.exec();

            return QHttpServerResponse("");
        });
    });

How can I use the WebSocket Connection without the QtConcurrent or how to keep the Websocket Connection open?

Thanks
Ronald

[Mr.Betatester]

I got it.

I need add a empty route that doesn't return a QHttpServerResponse. If i try to open a WS on a route that returns http data then the connection will be closed. Also if I use a non existing route.

Adding this route will do the magic:

m_httpServer.route("/notification", [](QHttpServerResponder&&) {});

[Christian Ehrlicher]

I don't see directly why it should be disconnected - apart from the strange (and imho wrong) std::unique_ptr<> stuff it looks fine.
Use a debugger to see why the disconect happens.

[Mr.Betatester]

@Mr-Betatester said in QHttpServer and WebSockets:

nextPendingWebSocketConnection

How can I use the WebSocket without the unique_ptr?
nextPendingWebSocketConnection returns a unique_ptr and I have to store it as unique_ptr otherwise it will be delete at function end.

https://doc-snapshots.qt.io/qt6-6.4/qabstracthttpserver.html#nextPendingWebSocketConnection

Thanks

[Christian Ehrlicher]

Sorry, I wasn't aware that they change it this way. Don't know why this was done though. So you have to work with it this way.

[Mr.Betatester]

I can use

QWebSocket* socket = m_httpServer.nextPendingWebSocketConnection().release();

and store a QWebSocket* in my m_clients.
But this doesn't fix the closed connection.

Without using the QtConcurrent Chrome close the connection with Code 1006.

[Christian Ehrlicher]

@Mr-Betatester said in QHttpServer and WebSockets:

and store a QWebSocket* in my m_clients.
But this doesn't fix the closed connection.

As I said it was my fault.

Use a debugger and see why the close happens.

[Mr.Betatester]

I got it.

I need add a empty route that doesn't return a QHttpServerResponse. If i try to open a WS on a route that returns http data then the connection will be closed. Also if I use a non existing route.

Adding this route will do the magic:

m_httpServer.route("/notification", [](QHttpServerResponder&&) {});

[ivanov.ivan]

@Mr-Betatester In Qt 6.5 webSocket with httpserver are not working. It inited but can't send messages.

[ivanov.ivan]

@ivanov-ivan At Qt 6.5.0 works code like this:

m_pHttpServer->route("/websocket/<arg>", [this](const QString &arg, const QHttpServerRequest) {
  qDebug() << __func__ << request  << arg;
  return QFuture<QHttpServerResponse>();
});