QWebSocketServer does not accept new connections

[Mark81]

Here my own implementation of a wrapper for a web socket communication:

#include "wsserver.h"
#include <QDebug>

#define DEBUG
const QString MODULE_ID = "[WSS]";

WsServer::WsServer(QObject *parent) : QObject(parent)
{
}

WsServer::~WsServer()
{
    qInfo() << MODULE_ID << "Closing connections";
    _wsServer->close();
}

void WsServer::listen(quint16 port)
{
    _wsServer = new QWebSocketServer("websocket", QWebSocketServer::NonSecureMode, this);
    if (_wsServer->listen(QHostAddress::Any, port))
    {
        qInfo() << MODULE_ID << "WebSocket server is listening on port" << port;
        connect(_wsServer, &QWebSocketServer::newConnection, this, &WsServer::newConnection);
        connect(_wsServer, &QWebSocketServer::closed, this, &WsServer::closed);
    }
}

void WsServer::sendTextMessage(QString message)
{
    foreach (QWebSocket *client, _listClients)
    {
        client->sendTextMessage(message);
    }
}

void WsServer::newConnection()
{
    QWebSocket *socket = _wsServer->nextPendingConnection();

    connect(socket, &QWebSocket::textMessageReceived, this, &WsServer::processTextMessage);
    connect(socket, &QWebSocket::binaryMessageReceived, this, &WsServer::processBinaryMessage);
    connect(socket, &QWebSocket::disconnected, this, &WsServer::socketDisconnected);
    _listClients.append(socket);
    emit clientConnected();

#ifdef DEBUG
    qInfo() << MODULE_ID << "New client connected" << socket << socket->peerAddress().toString() << QString("(%1)").arg(_listClients.size());
#endif
}

void WsServer::socketDisconnected()
{
    QWebSocket *socket = qobject_cast<QWebSocket *>(sender());
#ifdef DEBUG
    qInfo() << MODULE_ID << "Socket disconnected" << socket;
#endif
    if (socket)
    {
        _listClients.removeAll(socket);
        socket->deleteLater();
    }
}

void WsServer::processTextMessage(QString message)
{
#ifdef DEBUG
    qInfo() << MODULE_ID << "Text message received:" << message;
#endif
    emit textMessageReceived(message);
}

void WsServer::processBinaryMessage(QByteArray message)
{
#ifdef DEBUG
    qInfo() << MODULE_ID << "Binary message received:" << message;
#endif
    emit binaryMessageReceived(message);
}

It works fine and every time a client connects I get the related debug message.
When the browser changes (or reloads) the page I get the socket disconnected and just after the socket connected message.

As you can see, when a socket connects I print the number of clients currently connected:

qInfo() << MODULE_ID << "New client connected" << socket << socket->peerAddress().toString() << QString("(%1)").arg(_listClients.size());

and it's always 1, since I'm doing my tests with one browser only.
After changing/reloading the page some times the javascript websocket is not able to connect anymore.

In this situation if I close the application I get a long list of messages about new connections and disconnections. I guess there are the failed connections I've described above.

What's wrong here? What should I change in order to keep clean the socket list and allow the browser to always connect?

[SGaist]

Hi,

One thing that is missing is the error handling. You should add that to see if something else is going on.

[Mark81]

@SGaist I catch the following signals:

• WebSocket::error
• QWebSocketServer::acceptError
• QWebSocketServer::acceptError

and I was able to detect a CloseCodeBadOperation only when I refreshed the browser page very fast, nothing else.

This morning I launched my application and I connected a device to the websocket. Got the notification. Then I closed the browser. Got the notification.

Nothing else happened, but after few hours I tried again to connect but the javascript code timed out like above. No errors server side.

When I closed the application I got all the pending connection/disconnection notifications.

Please note that the browser and the server are on the same machine (I'm connecting as localhost).

Any hint would be very appreciated!

[SGaist]

Are you using multiple threads ?

[Mark81]

@SGaist not at all. At least, not in my code. I use these other classes in my application:

• QOpcUaProvider
• QOpcUaClient
• QOpcUaNode
• QSqlDatabase
• QSqlRecord

I don't know if they can interfere in any way with QWebSocketServer.

[SGaist]

I don't think they should.

Can you reduce your code a minimal example that still exhibits this behaviour ?