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Problem to bind a UDP socket.

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  • J jenya7
    25 Apr 2022, 11:09

    The bind method

    int UDP::Start(QString local_ip, quint16 local_port)
    {
        int result;
    
        //socket->reset();
        //socket->setProxy(QNetworkProxy::NoProxy);
            
        //result = socket->bind(QHostAddress::Any, local_port);
        result = socket->bind(QHostAddress(local_ip), local_port);
    
        QString err = socket->errorString();
    
        result = socket->error();
    
        return result;
    }
    

    In main

    int main(int argc, char *argv[])
    {
        QCoreApplication a(argc, argv);
    
        UDP udp_1 ;
    
        int soc_err;
        QString qs;
    
        QObject::connect(&udp_1, &UDP::ReadyForReader, &reader, &READER::ReadyForReader);
      
        GetNetInfo();
    
        soc_err = udp_1.Start("192.68.3.40", 8001);
    
        if (soc_err)
        {
            qs = QString::number(soc_err);
            cout << "Socket 1 error - " << qs.toStdString() << std::endl;
        }
        else
        {
            cout << "Socket 1 OK\n";
        }
    
        return a.exec();
    }
    

    I see in console
    192.168.3.40
    172.16.1.118
    127.0.0.1
    Socket 1 error - -1

    It sees the IP - 192.168.3.40 but I get an error. Why?

    C Offline
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    Christian Ehrlicher
    Lifetime Qt Champion
    wrote on 25 Apr 2022, 11:10 last edited by
    #2

    @jenya7 said in Problem to bind a UDP socket.:

    "192.68.3.40"

    Typo?

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    J 1 Reply Last reply 25 Apr 2022, 11:11
    0
    • C Christian Ehrlicher
      25 Apr 2022, 11:10

      @jenya7 said in Problem to bind a UDP socket.:

      "192.68.3.40"

      Typo?

      J Offline
      J Offline
      jenya7
      wrote on 25 Apr 2022, 11:11 last edited by
      #3

      @Christian-Ehrlicher said in Problem to bind a UDP socket.:

      @jenya7 said in Problem to bind a UDP socket.:

      "192.68.3.40"

      Typo?

      yes. it's "192.168.3.40"

      1 Reply Last reply
      0
      • C Offline
        C Offline
        Christian Ehrlicher
        Lifetime Qt Champion
        wrote on 25 Apr 2022, 11:18 last edited by
        #4

        So does it work now? If so please print out the errorString.

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        J 1 Reply Last reply 25 Apr 2022, 11:26
        0
        • C Christian Ehrlicher
          25 Apr 2022, 11:18

          So does it work now? If so please print out the errorString.

          J Offline
          J Offline
          jenya7
          wrote on 25 Apr 2022, 11:26 last edited by jenya7
          #5

          @Christian-Ehrlicher said in Problem to bind a UDP socket.:

          So does it work now? If so please print out the errorString.

          to print it I added another argument

          soc_err = udp_1.Start("192.168.3.40", 8001, &err_str);
          
              if (soc_err)
              {
                  qs = QString::number(soc_err);
                  cout << "Socket 1 error - " << qs.toStdString() << std::endl;
                  cout << err_str.toStdString();
              }
              else
              {
                  cout << "Socket 1 OK\n";
              }
          

          It prints
          192.168.3.40
          172.16.1.118
          127.0.0.1
          Socket 1 error - -1
          Unknown error

          this way

          result = socket->bind(QHostAddress::Any, local_port);
          

          I also get
          Socket 1 error - -1
          Unknown error

          C 1 Reply Last reply 25 Apr 2022, 11:30
          0
          • J jenya7
            25 Apr 2022, 11:26

            @Christian-Ehrlicher said in Problem to bind a UDP socket.:

            So does it work now? If so please print out the errorString.

            to print it I added another argument

            soc_err = udp_1.Start("192.168.3.40", 8001, &err_str);
            
                if (soc_err)
                {
                    qs = QString::number(soc_err);
                    cout << "Socket 1 error - " << qs.toStdString() << std::endl;
                    cout << err_str.toStdString();
                }
                else
                {
                    cout << "Socket 1 OK\n";
                }
            

            It prints
            192.168.3.40
            172.16.1.118
            127.0.0.1
            Socket 1 error - -1
            Unknown error

            this way

            result = socket->bind(QHostAddress::Any, local_port);
            

            I also get
            Socket 1 error - -1
            Unknown error

            C Offline
            C Offline
            Christian Ehrlicher
            Lifetime Qt Champion
            wrote on 25 Apr 2022, 11:30 last edited by
            #6

            @jenya7 said in Problem to bind a UDP socket.:

            172.16.1.118
            127.0.0.1

            Where do those two IPs come from? Please post your actual code and the real output. Also make sure the IPs you're using are correct (= your host has those IPs assigned)

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

            J 1 Reply Last reply 25 Apr 2022, 11:40
            0
            • C Christian Ehrlicher
              25 Apr 2022, 11:30

              @jenya7 said in Problem to bind a UDP socket.:

              172.16.1.118
              127.0.0.1

              Where do those two IPs come from? Please post your actual code and the real output. Also make sure the IPs you're using are correct (= your host has those IPs assigned)

              J Offline
              J Offline
              jenya7
              wrote on 25 Apr 2022, 11:40 last edited by jenya7
              #7

              @Christian-Ehrlicher said in Problem to bind a UDP socket.:

              @jenya7 said in Problem to bind a UDP socket.:

              172.16.1.118
              127.0.0.1

              Where do those two IPs come from? Please post your actual code and the real output. Also make sure the IPs you're using are correct (= your host has those IPs assigned)

              172.16.1.118 - is another network card. 127.0.0.1 - default local host.

              I changed for PC with only one network card.
              cmd->ipconfig
              Ethernet adapter Local Area Connection 2:

              Connection-specific DNS Suffix . :
              Link-local IPv6 Address . . . . . : fe80::7d2a:547e:e90a:6e3e%12
              IPv4 Address. . . . . . . . . . . : 172.16.1.139
              Subnet Mask . . . . . . . . . . . : 255.255.255.0
              Default Gateway . . . . . . . . . : 172.16.1.1

              soc_err = udp_1.Start("172.16.1.139", 8001, &err_str);
              

              I get
              172.16.1.139
              127.0.0.1
              Socket 1 error - -1
              Unknown error

              J 1 Reply Last reply 25 Apr 2022, 11:48
              0
              • J jenya7
                25 Apr 2022, 11:09

                The bind method

                int UDP::Start(QString local_ip, quint16 local_port)
                {
                    int result;
                
                    //socket->reset();
                    //socket->setProxy(QNetworkProxy::NoProxy);
                        
                    //result = socket->bind(QHostAddress::Any, local_port);
                    result = socket->bind(QHostAddress(local_ip), local_port);
                
                    QString err = socket->errorString();
                
                    result = socket->error();
                
                    return result;
                }
                

                In main

                int main(int argc, char *argv[])
                {
                    QCoreApplication a(argc, argv);
                
                    UDP udp_1 ;
                
                    int soc_err;
                    QString qs;
                
                    QObject::connect(&udp_1, &UDP::ReadyForReader, &reader, &READER::ReadyForReader);
                  
                    GetNetInfo();
                
                    soc_err = udp_1.Start("192.68.3.40", 8001);
                
                    if (soc_err)
                    {
                        qs = QString::number(soc_err);
                        cout << "Socket 1 error - " << qs.toStdString() << std::endl;
                    }
                    else
                    {
                        cout << "Socket 1 OK\n";
                    }
                
                    return a.exec();
                }
                

                I see in console
                192.168.3.40
                172.16.1.118
                127.0.0.1
                Socket 1 error - -1

                It sees the IP - 192.168.3.40 but I get an error. Why?

                K Offline
                K Offline
                KroMignon
                wrote on 25 Apr 2022, 11:42 last edited by
                #8

                @jenya7 said in Problem to bind a UDP socket.:

                result = socket->bind(QHostAddress(local_ip), local_port);
                QString err = socket->errorString();
                result = socket->error();
                

                This code do not make sense to me, you have to check if operation was not successful before trying to find an error!
                There is no error code "Success" in QAbstractSocket::SocketError (cf. https://doc.qt.io/qt-5/qabstractsocket.html#SocketError-enum).

                Please review your code.

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

                J 1 Reply Last reply 25 Apr 2022, 11:49
                2
                • J jenya7
                  25 Apr 2022, 11:40

                  @Christian-Ehrlicher said in Problem to bind a UDP socket.:

                  @jenya7 said in Problem to bind a UDP socket.:

                  172.16.1.118
                  127.0.0.1

                  Where do those two IPs come from? Please post your actual code and the real output. Also make sure the IPs you're using are correct (= your host has those IPs assigned)

                  172.16.1.118 - is another network card. 127.0.0.1 - default local host.

                  I changed for PC with only one network card.
                  cmd->ipconfig
                  Ethernet adapter Local Area Connection 2:

                  Connection-specific DNS Suffix . :
                  Link-local IPv6 Address . . . . . : fe80::7d2a:547e:e90a:6e3e%12
                  IPv4 Address. . . . . . . . . . . : 172.16.1.139
                  Subnet Mask . . . . . . . . . . . : 255.255.255.0
                  Default Gateway . . . . . . . . . : 172.16.1.1

                  soc_err = udp_1.Start("172.16.1.139", 8001, &err_str);
                  

                  I get
                  172.16.1.139
                  127.0.0.1
                  Socket 1 error - -1
                  Unknown error

                  J Offline
                  J Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on 25 Apr 2022, 11:48 last edited by
                  #9

                  @jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  J 1 Reply Last reply 25 Apr 2022, 11:53
                  0
                  • K KroMignon
                    25 Apr 2022, 11:42

                    @jenya7 said in Problem to bind a UDP socket.:

                    result = socket->bind(QHostAddress(local_ip), local_port);
                    QString err = socket->errorString();
                    result = socket->error();
                    

                    This code do not make sense to me, you have to check if operation was not successful before trying to find an error!
                    There is no error code "Success" in QAbstractSocket::SocketError (cf. https://doc.qt.io/qt-5/qabstractsocket.html#SocketError-enum).

                    Please review your code.

                    J Offline
                    J Offline
                    jenya7
                    wrote on 25 Apr 2022, 11:49 last edited by jenya7
                    #10

                    @KroMignon said in Problem to bind a UDP socket.:

                    @jenya7 said in Problem to bind a UDP socket.:

                    result = socket->bind(QHostAddress(local_ip), local_port);
                    QString err = socket->errorString();
                    result = socket->error();
                    

                    This code do not make sense to me, you have to check if operation was not successful before trying to find an error!
                    There is no error code "Success" in QAbstractSocket::SocketError (cf. https://doc.qt.io/qt-5/qabstractsocket.html#SocketError-enum).

                    Please review your code.

                    OK.

                    int UDP::Start(QString local_ip, quint16 local_port, QString *err_str)
                    {
                        int result;
                    
                        //socket->reset();
                        //socket->setProxy(QNetworkProxy::NoProxy);
                    
                        result = socket->bind(QHostAddress::Any, local_port);
                        //result = socket->bind(QHostAddress(local_ip), local_port);
                    
                        if (result != 0)
                        {
                            *err_str = socket->errorString();
                             result = socket->error();
                        }
                    
                        return result;
                    }
                    

                    So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
                    Should I trust to a returned result?

                    K 1 Reply Last reply 25 Apr 2022, 11:55
                    0
                    • J jsulm
                      25 Apr 2022, 11:48

                      @jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

                      J Offline
                      J Offline
                      jenya7
                      wrote on 25 Apr 2022, 11:53 last edited by
                      #11

                      @jsulm said in Problem to bind a UDP socket.:

                      @jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

                      can not do that.
                      it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                      QUdpSocket *socket;

                      C K 2 Replies Last reply 25 Apr 2022, 11:55
                      0
                      • J jenya7
                        25 Apr 2022, 11:49

                        @KroMignon said in Problem to bind a UDP socket.:

                        @jenya7 said in Problem to bind a UDP socket.:

                        result = socket->bind(QHostAddress(local_ip), local_port);
                        QString err = socket->errorString();
                        result = socket->error();
                        

                        This code do not make sense to me, you have to check if operation was not successful before trying to find an error!
                        There is no error code "Success" in QAbstractSocket::SocketError (cf. https://doc.qt.io/qt-5/qabstractsocket.html#SocketError-enum).

                        Please review your code.

                        OK.

                        int UDP::Start(QString local_ip, quint16 local_port, QString *err_str)
                        {
                            int result;
                        
                            //socket->reset();
                            //socket->setProxy(QNetworkProxy::NoProxy);
                        
                            result = socket->bind(QHostAddress::Any, local_port);
                            //result = socket->bind(QHostAddress(local_ip), local_port);
                        
                            if (result != 0)
                            {
                                *err_str = socket->errorString();
                                 result = socket->error();
                            }
                        
                            return result;
                        }
                        

                        So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
                        Should I trust to a returned result?

                        K Offline
                        K Offline
                        KroMignon
                        wrote on 25 Apr 2022, 11:55 last edited by
                        #12

                        @jenya7 said in Problem to bind a UDP socket.:

                        So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
                        Should I trust to a returned result?

                        Please take time to read a little bit of documentation. This will save you many of your time. It is very easy with Qt Creator, you only have to hit F1 to get help for a function!

                        QUdpSocket::bind() (cf. https://doc.qt.io/qt-5/qabstractsocket.html#bind) will return a boolean:

                        • true: success
                        • false: error

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

                        J 1 Reply Last reply 25 Apr 2022, 12:07
                        0
                        • J jenya7
                          25 Apr 2022, 11:53

                          @jsulm said in Problem to bind a UDP socket.:

                          @jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

                          can not do that.
                          it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                          QUdpSocket *socket;

                          C Offline
                          C Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on 25 Apr 2022, 11:55 last edited by
                          #13

                          @jenya7 said in Problem to bind a UDP socket.:

                          it's UDP socket, not Abstract socket.

                          QUdpSocket derives from QAbstractSocket...

                          udp_1.Start("192.168.3.40", 8001, &err_str);

                          You call Start() with an IP which you computer doesn't have according your ipconfig output above. This can't work. Also 172.16.1.118 is not your IP.

                          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
                          0
                          • J jenya7
                            25 Apr 2022, 11:53

                            @jsulm said in Problem to bind a UDP socket.:

                            @jenya7 Please connect a slot to https://doc.qt.io/qt-5/qabstractsocket.html#errorOccurred and print the error there.

                            can not do that.
                            it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                            QUdpSocket *socket;

                            K Offline
                            K Offline
                            KroMignon
                            wrote on 25 Apr 2022, 11:56 last edited by
                            #14

                            @jenya7 said in Problem to bind a UDP socket.:

                            it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                            QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
                            Do you know what subclassing means?

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

                            J 1 Reply Last reply 25 Apr 2022, 12:00
                            0
                            • K KroMignon
                              25 Apr 2022, 11:56

                              @jenya7 said in Problem to bind a UDP socket.:

                              it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                              QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
                              Do you know what subclassing means?

                              J Offline
                              J Offline
                              jenya7
                              wrote on 25 Apr 2022, 12:00 last edited by
                              #15

                              @KroMignon said in Problem to bind a UDP socket.:

                              @jenya7 said in Problem to bind a UDP socket.:

                              it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                              QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
                              Do you know what subclassing means?

                              QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);
                              
                              void UDP::SocketError(QAbstractSocket::SocketError socketError)
                              {
                                  qDebug() << "Socket Error: " << socketError;
                              }
                              

                              I get
                              error: no matching member function for call to 'connect'

                              C K 2 Replies Last reply 25 Apr 2022, 12:02
                              0
                              • J jenya7
                                25 Apr 2022, 12:00

                                @KroMignon said in Problem to bind a UDP socket.:

                                @jenya7 said in Problem to bind a UDP socket.:

                                it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                                QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
                                Do you know what subclassing means?

                                QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);
                                
                                void UDP::SocketError(QAbstractSocket::SocketError socketError)
                                {
                                    qDebug() << "Socket Error: " << socketError;
                                }
                                

                                I get
                                error: no matching member function for call to 'connect'

                                C Offline
                                C Offline
                                Christian Ehrlicher
                                Lifetime Qt Champion
                                wrote on 25 Apr 2022, 12:02 last edited by
                                #16

                                @jenya7 said in Problem to bind a UDP socket.:

                                QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);

                                And again to lazy to hit 'F1': https://doc.qt.io/qt-5/qabstractsocket-obsolete.html#error-1

                                Note: Signal error is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

                                connect(abstractSocket, QOverload<QAbstractSocket::SocketError>::of(&QAbstractSocket::error),
                                    [=](QAbstractSocket::SocketError socketError){ /* ... */ });
                                

                                Also this signal is deprecated - use errorOccurred() if possible (since Qt5.15)

                                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
                                2
                                • J jenya7
                                  25 Apr 2022, 12:00

                                  @KroMignon said in Problem to bind a UDP socket.:

                                  @jenya7 said in Problem to bind a UDP socket.:

                                  it's UDP socket, not Abstract socket. it has no errorOccurred signal.

                                  QUpdSocket is based on QAbstractSocket, do you have C++ knowledge?
                                  Do you know what subclassing means?

                                  QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);
                                  
                                  void UDP::SocketError(QAbstractSocket::SocketError socketError)
                                  {
                                      qDebug() << "Socket Error: " << socketError;
                                  }
                                  

                                  I get
                                  error: no matching member function for call to 'connect'

                                  K Offline
                                  K Offline
                                  KroMignon
                                  wrote on 25 Apr 2022, 12:02 last edited by KroMignon
                                  #17

                                  @jenya7 said in Problem to bind a UDP socket.:

                                  QObject::connect(socket, &QAbstractSocket::error, this, &UDP::SocketError);

                                  This signal is called errorOccurred() and not error()

                                  [EDIT] errorOccurred() has been added with Qt 5.15, if you are using an older Qt version, use code suggested by @Christian-Ehrlicher

                                  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
                                  • K KroMignon
                                    25 Apr 2022, 11:55

                                    @jenya7 said in Problem to bind a UDP socket.:

                                    So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
                                    Should I trust to a returned result?

                                    Please take time to read a little bit of documentation. This will save you many of your time. It is very easy with Qt Creator, you only have to hit F1 to get help for a function!

                                    QUdpSocket::bind() (cf. https://doc.qt.io/qt-5/qabstractsocket.html#bind) will return a boolean:

                                    • true: success
                                    • false: error
                                    J Offline
                                    J Offline
                                    jenya7
                                    wrote on 25 Apr 2022, 12:07 last edited by
                                    #18

                                    @KroMignon said in Problem to bind a UDP socket.:

                                    @jenya7 said in Problem to bind a UDP socket.:

                                    So I get result = 1 after result = socket->bind(QHostAddress::Any, local_port);
                                    Should I trust to a returned result?

                                    Please take time to read a little bit of documentation. This will save you many of your time. It is very easy with Qt Creator, you only have to hit F1 to get help for a function!

                                    QUdpSocket::bind() (cf. https://doc.qt.io/qt-5/qabstractsocket.html#bind) will return a boolean:

                                    • true: success
                                    • false: error

                                    oops. sorry.

                                    1 Reply Last reply
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