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IPC with QLocalSocket UnconnectedState not called

  • Hi,

    I am having a weird issue with QLocalSocket while trying to communicate between two applications. This is my first time using QLocalSocket. I have subclassed a QLocalSocket and use moveToThread() to have all of my packet parsing done in the background. The stateChanged() signal connected like so in my QMainWindow:
    // local socket class
    socket = new LocalSocket();
    connect(socket, SIGNAL(stateChanged(QLocalSocket::LocalSocketState)), this, SLOT(socketStateChanged(QLocalSocket::LocalSocketState)));

    ... other connections to connect to the server, send recv data, ect.

    // local socket thread
    socketThread = new QThread(this);
    socket->moveToThread(socketThread);   // move the socket subclass to the thread
    socketThread->start();  // start the thread


    where my slot is as follows:
    // socket state changed (private slot)
    void MainWindow::socketStateChanged(QLocalSocket::LocalSocketState state)
    // check the socket state
    switch (state){
    // unconnected state
    case QLocalSocket::UnconnectedState: {
    // start the timer to connect
    if (!timerConnection->isActive())

            // set disconnected ui
        // connected state
        case QLocalSocket::ConnectedState: {
            // set the connected ui


    I get the QLocalSocket::ConnectingState and QLocalSocket::ConnectedState initially after I call connectToServer() (which both sides start data transmission successfully), but when I kill the process running the server, I never receive a QLocalSocket::UnconnectedState.

    I know in Linux, the QLocalSocket uses a file in /tmp/'server_name' for the IPC, is there something on the server side that needs to happen when the server cleanup happens? (after the process is killed)

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