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QTcpSocket, execution halts why and what does it mean?

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  • KroMignonK KroMignon

    @SPlatten said in QTcpSocket, execution halts why and what does it mean?:

    can you please help me with an example?

    Yes, but an example for doing what exactly?

    SPlattenS Offline
    SPlattenS Offline
    SPlatten
    wrote on last edited by SPlatten
    #9

    @KroMignon , the examples I've found on QThread do not include how to NOT block the event loop, so an example on what to do in the thread so it doesn't block the event loop.

    I've just added:

            QCoreApplication::processEvents();
    

    To the thread loops, is this enough?

    Kind Regards,
    Sy

    KroMignonK Pl45m4P 2 Replies Last reply
    0
    • SPlattenS SPlatten

      @KroMignon , do you mean isn't ?

      Links:

      https://doc.qt.io/qt-5/qabstractsocket.html#waitForConnected
      https://www.bogotobogo.com/Qt/Qt5_QTcpSocket.php

      There are many more.

      Pl45m4P Offline
      Pl45m4P Offline
      Pl45m4
      wrote on last edited by
      #10

      @SPlatten

      In general you can say that

      • for(;;){}
      • while(1)
      • while(true) <- this is what you are doing basically

      are pure evil, when used together with Qt GUI Framework. There might be some exceptions (esp. plain C++ code) but it's not safe to use it, when having signals&slots + events in use.

      In your linked example this

      if (socket->waitForConnected(1000))
      

      for example, wont block the event loop forever, if this is what you were thinking.


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

      ~E. W. Dijkstra

      SPlattenS 1 Reply Last reply
      0
      • Pl45m4P Pl45m4

        @SPlatten

        In general you can say that

        • for(;;){}
        • while(1)
        • while(true) <- this is what you are doing basically

        are pure evil, when used together with Qt GUI Framework. There might be some exceptions (esp. plain C++ code) but it's not safe to use it, when having signals&slots + events in use.

        In your linked example this

        if (socket->waitForConnected(1000))
        

        for example, wont block the event loop forever, if this is what you were thinking.

        SPlattenS Offline
        SPlattenS Offline
        SPlatten
        wrote on last edited by
        #11

        @Pl45m4, I wasn't trying to block the event loop.

        Kind Regards,
        Sy

        1 Reply Last reply
        0
        • SPlattenS SPlatten

          @KroMignon , the examples I've found on QThread do not include how to NOT block the event loop, so an example on what to do in the thread so it doesn't block the event loop.

          I've just added:

                  QCoreApplication::processEvents();
          

          To the thread loops, is this enough?

          KroMignonK Offline
          KroMignonK Offline
          KroMignon
          wrote on last edited by KroMignon
          #12

          @SPlatten said in QTcpSocket, execution halts why and what does it mean?:

          To the thread loops, is this enough?

          I am not sure, is clsMsgSender a QThread or a QObject?

          @SPlatten I will try to share with you how I use QTcpSocket.

          First, there is no need to create a thread for that, the easiest implementation is (for me):

          // supposing mSocket is a member of the current class
          mSocket = new QTcpSocket();
          
          // remove TCP delay
          mSocket->setSocketOption(QAbstractSocket::LowDelayOption, 1);
          
          QObject::connect(mSocket, &QAbstractSocket::connected,
                           [this]()
                           {
                              qDebug() << "Connected with" << mSocket->peerPort();
                              // Do stuff here                  
                           });
          QObject::connect(mSocket, &QAbstractSocket::disconnected,
                           [this]()
                           {
                              qDebug() << "Disconnected from" << mSocket->peerPort();
                              mSocket->delateLater();
                              mSocket = nullptr;
                           });
          QObject::connect(mSocket, &QIODevice::bytesWritten,
                           [this](qint64 bytes)
                           {
                              qDebug() << bytes << "send to " << mSocket->peerPort();
                              // do stuff (add next data?)
                           });
                           
          mSocket->connectToHost(remoteIp, tcpPort);
          QObject::connect(mSocket, &QIODevice::readyRead, [this](){
              auto buffer = mSocket->readAll();
              qDebug() << "receiving" << buffer.size() << "bytes from" << mSocket->peerPort();
              // do stuff with data
          });
          

          It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

          1 Reply Last reply
          1
          • SPlattenS SPlatten

            @KroMignon , the examples I've found on QThread do not include how to NOT block the event loop, so an example on what to do in the thread so it doesn't block the event loop.

            I've just added:

                    QCoreApplication::processEvents();
            

            To the thread loops, is this enough?

            Pl45m4P Offline
            Pl45m4P Offline
            Pl45m4
            wrote on last edited by Pl45m4
            #13

            @SPlatten said in QTcpSocket, execution halts why and what does it mean?:

            the examples I've found on QThread do not include how to NOT block the event loop

            Here, this wont block:

            • https://www.bogotobogo.com/Qt/Qt5_QTcpSocket.php (your 2nd linked example)

            This guy (https://stackoverflow.com/questions/37167927/proper-way-to-run-managable-background-thread-with-qthread) has made a similar mistake.
            You want to connect once and then let the event loop and your signals do the rest.


            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
            1
            • Christian EhrlicherC Offline
              Christian EhrlicherC Offline
              Christian Ehrlicher
              Lifetime Qt Champion
              wrote on last edited by
              #14

              Funny - this discussion was already done more than 3 months ago already: https://forum.qt.io/topic/120700/receiving-data-from-qtcpsocket/30

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

              SPlattenS 1 Reply Last reply
              2
              • Christian EhrlicherC Christian Ehrlicher

                Funny - this discussion was already done more than 3 months ago already: https://forum.qt.io/topic/120700/receiving-data-from-qtcpsocket/30

                SPlattenS Offline
                SPlattenS Offline
                SPlatten
                wrote on last edited by
                #15

                @Christian-Ehrlicher , is it any surprise I'm confused, in that thread you pointed me to the Fortune client and server examples, which I have been following then there is conflicting advice that comes back form this forum when I implement a solution that I'm having problems with.

                Add to this the what appears to be flaky Qt Creator with updates that seem to send me backwards. I feel I'm loosing the plot.

                Kind Regards,
                Sy

                1 Reply Last reply
                0
                • Christian EhrlicherC Offline
                  Christian EhrlicherC Offline
                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on last edited by
                  #16

                  The old thread told you to use signals and slots and not the waitFor functions and now we're at the exactly same place.

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

                  SPlattenS 2 Replies Last reply
                  0
                  • Christian EhrlicherC Christian Ehrlicher

                    The old thread told you to use signals and slots and not the waitFor functions and now we're at the exactly same place.

                    SPlattenS Offline
                    SPlattenS Offline
                    SPlatten
                    wrote on last edited by SPlatten
                    #17

                    @Christian-Ehrlicher , well obviously I have mental memory issues.

                    Kind Regards,
                    Sy

                    1 Reply Last reply
                    0
                    • Christian EhrlicherC Christian Ehrlicher

                      The old thread told you to use signals and slots and not the waitFor functions and now we're at the exactly same place.

                      SPlattenS Offline
                      SPlattenS Offline
                      SPlatten
                      wrote on last edited by
                      #18

                      @Christian-Ehrlicher , the examples that ship with Qt 5.15.2 include:

                      blockingfortuneclient
                      threadedfortuneserver

                      On looking at both, these are the sources I used to base my work on. My server is slightly different in that the clients are intended to stay connected after establishing a connection.

                      I will compare the client source with my own.

                      Kind Regards,
                      Sy

                      1 Reply Last reply
                      0
                      • Christian EhrlicherC Offline
                        Christian EhrlicherC Offline
                        Christian Ehrlicher
                        Lifetime Qt Champion
                        wrote on last edited by
                        #19

                        From my pov you don't need threads at all but this is not what you want to hear for whatever reason - you rather work on simple stuff like a QTcpSocket for months.

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

                        SPlattenS 1 Reply Last reply
                        0
                        • Christian EhrlicherC Christian Ehrlicher

                          From my pov you don't need threads at all but this is not what you want to hear for whatever reason - you rather work on simple stuff like a QTcpSocket for months.

                          SPlattenS Offline
                          SPlattenS Offline
                          SPlatten
                          wrote on last edited by
                          #20

                          @Christian-Ehrlicher , one day I will be ready to share what I'm working on, which isn't now.

                          Kind Regards,
                          Sy

                          KroMignonK 1 Reply Last reply
                          0
                          • SPlattenS SPlatten

                            @Christian-Ehrlicher , one day I will be ready to share what I'm working on, which isn't now.

                            KroMignonK Offline
                            KroMignonK Offline
                            KroMignon
                            wrote on last edited by
                            #21

                            @SPlatten said in QTcpSocket, execution halts why and what does it mean?:

                            one day I will be ready to share what I'm working on, which isn't now.

                            This sentence sounds strange to me.

                            I think you misunderstanding some comments/replies you received here.
                            My personal goal is to help other developers to solve problem they have will creating software with Qt, like I received help from other to solve/understand errors in my software.

                            On the other side, this also helps me to get a better overview of Qt Framework and continue to learn.

                            It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                            SPlattenS Pl45m4P 2 Replies Last reply
                            1
                            • KroMignonK KroMignon

                              @SPlatten said in QTcpSocket, execution halts why and what does it mean?:

                              one day I will be ready to share what I'm working on, which isn't now.

                              This sentence sounds strange to me.

                              I think you misunderstanding some comments/replies you received here.
                              My personal goal is to help other developers to solve problem they have will creating software with Qt, like I received help from other to solve/understand errors in my software.

                              On the other side, this also helps me to get a better overview of Qt Framework and continue to learn.

                              SPlattenS Offline
                              SPlattenS Offline
                              SPlatten
                              wrote on last edited by
                              #22

                              @KroMignon , sorry, some of the comments, not yours I find a little offensive.

                              Kind Regards,
                              Sy

                              1 Reply Last reply
                              0
                              • KroMignonK KroMignon

                                @SPlatten said in QTcpSocket, execution halts why and what does it mean?:

                                one day I will be ready to share what I'm working on, which isn't now.

                                This sentence sounds strange to me.

                                I think you misunderstanding some comments/replies you received here.
                                My personal goal is to help other developers to solve problem they have will creating software with Qt, like I received help from other to solve/understand errors in my software.

                                On the other side, this also helps me to get a better overview of Qt Framework and continue to learn.

                                Pl45m4P Offline
                                Pl45m4P Offline
                                Pl45m4
                                wrote on last edited by
                                #23

                                @KroMignon said in QTcpSocket, execution halts why and what does it mean?:

                                My personal goal is to help other developers to solve problem they have will creating software with Qt, like I received help from other to solve/understand errors in my software.
                                On the other side, this also helps me to get a better overview of Qt Framework and continue to learn.

                                This is exactly why I'm here :D


                                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
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