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Problem to bind a UDP socket.

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  • J Offline
    J Offline
    jenya7
    wrote on last edited by
    #1

    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?

    Christian EhrlicherC KroMignonK 2 Replies Last reply
    0
    • J jenya7

      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?

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

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

      "192.68.3.40"

      Typo?

      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
      0
      • Christian EhrlicherC Christian Ehrlicher

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

        "192.68.3.40"

        Typo?

        J Offline
        J Offline
        jenya7
        wrote on 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
        • Christian EhrlicherC Offline
          Christian EhrlicherC Offline
          Christian Ehrlicher
          Lifetime Qt Champion
          wrote on last edited by
          #4

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

          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
          0
          • Christian EhrlicherC Christian Ehrlicher

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

            J Offline
            J Offline
            jenya7
            wrote on 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

            Christian EhrlicherC 1 Reply Last reply
            0
            • J jenya7

              @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

              Christian EhrlicherC Offline
              Christian EhrlicherC Offline
              Christian Ehrlicher
              Lifetime Qt Champion
              wrote on 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
              0
              • Christian EhrlicherC Christian Ehrlicher

                @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 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

                jsulmJ 1 Reply Last reply
                0
                • J jenya7

                  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?

                  KroMignonK Offline
                  KroMignonK Offline
                  KroMignon
                  wrote on 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
                  2
                  • J jenya7

                    @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

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on 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
                    0
                    • KroMignonK KroMignon

                      @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 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?

                      KroMignonK 1 Reply Last reply
                      0
                      • jsulmJ jsulm

                        @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 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;

                        Christian EhrlicherC KroMignonK 2 Replies Last reply
                        0
                        • J jenya7

                          @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?

                          KroMignonK Offline
                          KroMignonK Offline
                          KroMignon
                          wrote on 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
                          0
                          • J jenya7

                            @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;

                            Christian EhrlicherC Offline
                            Christian EhrlicherC Offline
                            Christian Ehrlicher
                            Lifetime Qt Champion
                            wrote on 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

                              @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;

                              KroMignonK Offline
                              KroMignonK Offline
                              KroMignon
                              wrote on 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
                              0
                              • KroMignonK KroMignon

                                @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 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'

                                Christian EhrlicherC KroMignonK 2 Replies Last reply
                                0
                                • J jenya7

                                  @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'

                                  Christian EhrlicherC Offline
                                  Christian EhrlicherC Offline
                                  Christian Ehrlicher
                                  Lifetime Qt Champion
                                  wrote on 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

                                    @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'

                                    KroMignonK Offline
                                    KroMignonK Offline
                                    KroMignon
                                    wrote on 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
                                    • KroMignonK KroMignon

                                      @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 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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