QTcpServer not receiving any data when working in QRunnable

Question

What I'm having is a strange problem in typical scenario: QTcpServer's method incomingConnection is overrided in custom class, and any received connection is planned for processing in separate thread on QThreadPool.

Server:

void FooS::incomingConnection(qintptr socketDescriptor)
{

    QThreadPool *thread_pool = QThreadPool::globalInstance();
    FooSocket *fs = new FooSocket();
    fs->setSocket(socketDescriptor);
    thread_pool->start(fs);
}

Task:

class FooSocket: public QObject, public QRunnable;
...
private slots:
   void connectionIncomingData();
...
void FooSocket::run() {
    QTcpSocket *socket = new QTcpSocket();
    qDebug() << "SD: " << socketDescriptor; // is correct
    if (!socket->setSocketDescriptor(socketDescriptor)) {
        qDebug() << "Can't set socket descriptor";
        emit error(socket->error());
        return;
    }
//  -- had no effect here
// socket->moveToThread(QThread::currentThread()); 

    connect(socket, SIGNAL(readyRead()), this, SLOT(connectionIncomingData()));
    connect(socket, SIGNAL(disconnected()), this, SLOT(connectionClosed()));    

}

readyRead signal doesn't gets triggered, but socket client is confirmed (tcpdump) to send data..

After making QRunnable to spawn a QThread object with socket logics inside, and toying with setAutoDelete, moveToThread - still no effect.

Answer 1

In order to process events in a QRunnable, a thread needs to have its own event loop, it mustn't rely on the one from the main thread. From what you've shown in your code, your thread quickly starts, then exits without running a loop.

Try adding

QEventLoop loop;

// connect a signal to the event loop's quit() slot

loop.exec();