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unsync function , QSocketNotifier & Cannot move to target thread

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  • _ __d4ve__

    Hi ,

    Here is the flow of tray Icon app syncing with server and the problem.

    Client* client = Client::instance();  // Singleton instance of Client
    
    • Client instance created on main()
    QAction::connect(actionSync, &QAction::triggered, clickHandler, &MenuClickHandler::syncApplication);
    
    • actionSync triggers MenuClickHandler::syncApplication

    • syncApplication()

    • initSync() runs and connects to the server

    The notification i get is :

    QSocketNotifier: Socket notifiers cannot be enabled or disabled from another thread
    
    void MenuClickHandler::syncApplication()
    {
    
        QThread* thread  = new QThread(this);
        Client::instance()->moveToThread(thread);
    
        if(Client::instance()->sync)
        {
            thread->quit();
            Client::instance()->disconnectSync();
            return;
        }
    
        connect(thread, &QThread::started, [=](){
            qDebug() << "Thread started - syncApplication";
            //Client client;
            Client::instance()->initSync();
    
            while (Client::instance()->sync == true) {
                qDebug() << "Data Receiving loop.";
                qDebug() << "Client->sync = " << Client::instance()->sync;
                Client::instance()->DataReceived();
            }
    
            // Emit a finished signal to allow thread cleanup
            thread->quit();
        });
    
        connect(thread, &QThread::finished, thread, &QThread::deleteLater);
    
        thread->start();
    }
    

    Here is some output :

    From main()

    Client thread: QThread(0x19f82244350)
    Current thread: QThread(0x19f82244350)
    

    From syncAppliaction()

    Thread started - syncApplication
    

    From initSync()

    sync request sent.
    QObject: Cannot create children for a parent that is in a different thread.
    (Parent is QTcpSocket(0x19f82251780), parent's thread is QThread(0x19f82244350), current thread is QThread(0x19f822c4660)
    

    everything works but with this notifications/errors

    I can't figure out how I should troubleshot that ?

    Christian EhrlicherC Offline
    Christian EhrlicherC Offline
    Christian Ehrlicher
    Lifetime Qt Champion
    wrote on last edited by
    #2

    @__d4ve__ said in unsync function , QSocketNotifier & Cannot move to target thread:

    can't figure out how I should troubleshot that ?

    Don't use a global static, don't use threads at all because they are not needed here.

    Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
    Visit the Qt Academy at https://academy.qt.io/catalog

    1 Reply Last reply
    1
    • _ Offline
      _ Offline
      __d4ve__
      wrote on last edited by
      #3

      GUI will be unresponsive other wise , why not using global static ?

      Christian EhrlicherC 1 Reply Last reply
      0
      • _ __d4ve__

        GUI will be unresponsive other wise , why not using global static ?

        Christian EhrlicherC Offline
        Christian EhrlicherC Offline
        Christian Ehrlicher
        Lifetime Qt Champion
        wrote on last edited by
        #4

        @__d4ve__ said in unsync function , QSocketNotifier & Cannot move to target thread:

        GUI will be unresponsive other wise

        Use signals and slots and a/or a QTimer. No need to block anything.
        Globlals, especially QObject one are bad design.

        Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
        Visit the Qt Academy at https://academy.qt.io/catalog

        1 Reply Last reply
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        • _ Offline
          _ Offline
          __d4ve__
          wrote on last edited by
          #5

          Ok ,
          signals and slots ,
          I have Client variable that supposed to be global variable and used in another classes

          1 Reply Last reply
          0
          • _ Offline
            _ Offline
            __d4ve__
            wrote on last edited by
            #6

            Used QTimer , makes GUI freeze :

            void MenuClickHandler::syncApplication()
            {
                if(Client::instance()->sync)
                {
                    Client::instance()->disconnectSync();
                    return;
                }
            
                QTimer* timer = new QTimer(this);  // Use a timer instead of a new thread
            
                connect(timer, &QTimer::timeout, [=](){
            
                    Client::instance()->initSync();
            
                    while (Client::instance()->sync == true) {
                        qDebug() << "Data Receiving loop.";
                        qDebug() << "Client->sync = " << Client::instance()->sync;
                        Client::instance()->DataReceived();
                    }
            
                    });
                    timer->start(1000);
            }
            

            I can see that something wrong with the design but as far as i know Qt usage , Qthreads or instance() I would like to hear what other options there , if i Initiate object on main() , what's the right way to connect it ?

            I have QAction on main()

            QAction::connect(actionSync, &QAction::triggered, clickHandler, &MenuClickHandler::syncApplication);
            

            that changes it label to 'unsync' after successful syncing another click should unsync it .
            this scenario may confuse so what should be done with signal slot ?

            first click syncs
            the second unsyncs ( on successful synced client only )
            recommended not using Qthreads , Client instance()

            Christian EhrlicherC 1 Reply Last reply
            0
            • _ __d4ve__

              Used QTimer , makes GUI freeze :

              void MenuClickHandler::syncApplication()
              {
                  if(Client::instance()->sync)
                  {
                      Client::instance()->disconnectSync();
                      return;
                  }
              
                  QTimer* timer = new QTimer(this);  // Use a timer instead of a new thread
              
                  connect(timer, &QTimer::timeout, [=](){
              
                      Client::instance()->initSync();
              
                      while (Client::instance()->sync == true) {
                          qDebug() << "Data Receiving loop.";
                          qDebug() << "Client->sync = " << Client::instance()->sync;
                          Client::instance()->DataReceived();
                      }
              
                      });
                      timer->start(1000);
              }
              

              I can see that something wrong with the design but as far as i know Qt usage , Qthreads or instance() I would like to hear what other options there , if i Initiate object on main() , what's the right way to connect it ?

              I have QAction on main()

              QAction::connect(actionSync, &QAction::triggered, clickHandler, &MenuClickHandler::syncApplication);
              

              that changes it label to 'unsync' after successful syncing another click should unsync it .
              this scenario may confuse so what should be done with signal slot ?

              first click syncs
              the second unsyncs ( on successful synced client only )
              recommended not using Qthreads , Client instance()

              Christian EhrlicherC Offline
              Christian EhrlicherC Offline
              Christian Ehrlicher
              Lifetime Qt Champion
              wrote on last edited by
              #7

              @__d4ve__ said in unsync function , QSocketNotifier & Cannot move to target thread:

              while (Client::instance()->sync == true) {

              I mean -what do you expect when you block the event loop... let Client emit a signal when the data was received.

              Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
              Visit the Qt Academy at https://academy.qt.io/catalog

              1 Reply Last reply
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              • _ Offline
                _ Offline
                __d4ve__
                wrote on last edited by
                #8

                Changed the code but the GUI still not responsive :

                void MenuClickHandler::syncApplication()
                {
                    qDebug() << Client::instance()->socket->isOpen() ;
                    if(Client::instance()->sync && Client::instance()->socket->isOpen() )
                    {
                        Client::instance()->disconnectSync();
                        return;
                    }
                
                    QTimer* timer = new QTimer(this);  // Use a timer instead of a new thread
                
                    connect(timer, &QTimer::timeout, [=](){
                
                        Client::instance()->initSync();
                
                        while (Client::instance()->sync == true) {
                            qDebug() << "Data Receiving loop.";
                            qDebug() << "Client->sync = " << Client::instance()->sync;
                            Client::instance()->DataReceived();
                        }
                
                        });
                        timer->start(1000);
                }
                

                Syncs successfully but not responsive afterwards

                Pl45m4P 1 Reply Last reply
                0
                • _ __d4ve__

                  Changed the code but the GUI still not responsive :

                  void MenuClickHandler::syncApplication()
                  {
                      qDebug() << Client::instance()->socket->isOpen() ;
                      if(Client::instance()->sync && Client::instance()->socket->isOpen() )
                      {
                          Client::instance()->disconnectSync();
                          return;
                      }
                  
                      QTimer* timer = new QTimer(this);  // Use a timer instead of a new thread
                  
                      connect(timer, &QTimer::timeout, [=](){
                  
                          Client::instance()->initSync();
                  
                          while (Client::instance()->sync == true) {
                              qDebug() << "Data Receiving loop.";
                              qDebug() << "Client->sync = " << Client::instance()->sync;
                              Client::instance()->DataReceived();
                          }
                  
                          });
                          timer->start(1000);
                  }
                  

                  Syncs successfully but not responsive afterwards

                  Pl45m4P Offline
                  Pl45m4P Offline
                  Pl45m4
                  wrote on last edited by
                  #9

                  @__d4ve__ said in unsync function , QSocketNotifier & Cannot move to target thread:

                  connect(timer, &QTimer::timeout, ={

                      Client::instance()->initSync();
                  
                      while (Client::instance()->sync == true) {
                          qDebug() << "Data Receiving loop.";
                          qDebug() << "Client->sync = " << Client::instance()->sync;
                          Client::instance()->DataReceived();
                      }
                  
                      });
                      timer->start(1000);
                  

                  I think the while loop is still blocking.

                  So better something like

                  QTimer::singleShot(0, this, ()[=]{
                  
                  // sync here
                  
                  });
                  

                  If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                  ~E. W. Dijkstra

                  1 Reply Last reply
                  0
                  • _ Offline
                    _ Offline
                    __d4ve__
                    wrote on last edited by
                    #10

                    The problem with SingleShot function is that its good as written for 'single shot' what makes the app not responsive as desired in period of times.

                    I changed program design and currently sync loop runs on SingleShot but I need alternative
                    not using QThreads and while loop leaves me with maybe connect on some terms

                    I have :

                    sync(): init connection

                    connection_loop() : maintains connection

                    receiveData() : receives data from server

                    Christian EhrlicherC 1 Reply Last reply
                    0
                    • _ __d4ve__

                      The problem with SingleShot function is that its good as written for 'single shot' what makes the app not responsive as desired in period of times.

                      I changed program design and currently sync loop runs on SingleShot but I need alternative
                      not using QThreads and while loop leaves me with maybe connect on some terms

                      I have :

                      sync(): init connection

                      connection_loop() : maintains connection

                      receiveData() : receives data from server

                      Christian EhrlicherC Offline
                      Christian EhrlicherC Offline
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      @__d4ve__ said in unsync function , QSocketNotifier & Cannot move to target thread:

                      connection_loop() : maintains connection

                      What does this mean? What has to be done in there? A keep-alive every n seconds? Use a QTimer.

                      receiveData() : receives data from server

                      Use the readyRead() signal and process your data.

                      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                      Visit the Qt Academy at https://academy.qt.io/catalog

                      1 Reply Last reply
                      1
                      • _ Offline
                        _ Offline
                        __d4ve__
                        wrote on last edited by __d4ve__
                        #12

                        I use socket->waitForReadyRead(1000); instead readyRead() and yes connection_loop() does keep-alive every n seconds but I look for something more responsive

                        Christian EhrlicherC 1 Reply Last reply
                        0
                        • _ __d4ve__

                          I use socket->waitForReadyRead(1000); instead readyRead() and yes connection_loop() does keep-alive every n seconds but I look for something more responsive

                          Christian EhrlicherC Offline
                          Christian EhrlicherC Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on last edited by
                          #13

                          @__d4ve__ said in unsync function , QSocketNotifier & Cannot move to target thread:

                          I use socket->waitForReadyRead(1000);

                          Again: do not block the event loop, use signals and slots.

                          Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                          Visit the Qt Academy at https://academy.qt.io/catalog

                          1 Reply Last reply
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