QUdpsocket send and receive broadcast in linux

[danics]

I try to write a QUdpsocket for read and write on braodcast address. following code work in windows with Qt5 library but don't work on my CentOs with Qt4.6, (i haven't any error in CentOs just don't read anything)

configure qudpsocket

iface = "";
 
    QList<QNetworkInterface> ifaces = QNetworkInterface::allInterfaces();
       foreach (QNetworkInterface nf, ifaces) {
           if(nf.name() == iface || iface.isNull() || iface.isEmpty())
           {
               if(nf.flags() & QNetworkInterface::CanBroadcast)
               {
                   foreach (QNetworkAddressEntry na, nf.addressEntries()) {
                       if(na.broadcast().toString() != "") {
                           send_to = na.broadcast().toIPv4Address();
                           bind_to = na.ip().toIPv4Address();
                           hostname = na.ip().toString();
                           if (verbose)
                               qDebug("using address=%s broadcast=%s",
                                          na.ip().toString().toLocal8Bit().data(), na.broadcast().toString().toLocal8Bit().data());
                           break;
                       }
                   }
               }
           }
           if(hostname != "") break;
       }
 
       if(bind_to)
       {
               broadcast.setAddress(send_to);
        #ifdef Q_OS_WIN
               QHostAddress address(bind_to);
        #elif defined(Q_OS_LINUX)
               QHostAddress address(send_to); // dont work on centos Qt 4.7
        #endif
 
               if(!udpsock.bind(address, port_nbr, QUdpSocket::ShareAddress
                         | QUdpSocket::ReuseAddressHint))
                      qFatal("bind udp");
 
               if(verbose)
                      qDebug() << "configured, hostname=" << hostname;
       }

iface = "";

    QList<QNetworkInterface> ifaces = QNetworkInterface::allInterfaces();
       foreach (QNetworkInterface nf, ifaces) {
           if(nf.name() == iface || iface.isNull() || iface.isEmpty())
           {
               if(nf.flags() & QNetworkInterface::CanBroadcast)
               {
                   foreach (QNetworkAddressEntry na, nf.addressEntries()) {
                       if(na.broadcast().toString() != "") {
                           send_to = na.broadcast().toIPv4Address();
                           bind_to = na.ip().toIPv4Address();
                           hostname = na.ip().toString();
                           if (verbose)
                               qDebug("using address=%s broadcast=%s",
                                          na.ip().toString().toLocal8Bit().data(), na.broadcast().toString().toLocal8Bit().data());
                           break;
                       }
                   }
               }
           }
           if(hostname != "") break;
       }

       if(bind_to)
       {
               broadcast.setAddress(send_to);
        #ifdef Q_OS_WIN
               QHostAddress address(bind_to);
        #elif defined(Q_OS_LINUX)
               QHostAddress address(send_to); // dont work on centos Qt 4.7
        #endif

               if(!udpsock.bind(address, port_nbr, QUdpSocket::ShareAddress
                         | QUdpSocket::ReuseAddressHint))
                      qFatal("bind udp");

               if(verbose)
                      qDebug() << "configured, hostname=" << hostname;
       }

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loop for listening

int handleUdp() {
       if(!udpsock.hasPendingDatagrams()) return -1;
       char data[1024];
       QHostAddress peerAddress;
 
       int rsize = udpsock.readDatagram(data, 1024, &peerAddress);
       if(rsize <= 0) return -1;
       .....
       return 0;
    }
 
    while(!terminated) {
        ...
        if(udpsock.waitForReadyRead(2000))
           handleUdp();
        ...
        // end of each loop broadcast data
        udpsock.writeDatagram(data(), broadcast, port_nbr)
    }

int handleUdp() {
       if(!udpsock.hasPendingDatagrams()) return -1;
       char data[1024];
       QHostAddress peerAddress;

       int rsize = udpsock.readDatagram(data, 1024, &peerAddress);
       if(rsize <= 0) return -1;
       .....
       return 0;
    }

    while(!terminated) {
        ...
        if(udpsock.waitForReadyRead(2000))
           handleUdp();
        ...
        // end of each loop broadcast data
        udpsock.writeDatagram(data(), broadcast, port_nbr)
    }

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this is debug information:

using address=123.123.1.14 broadcast=123.255.255.255
configured, hostname=123.123.1.14