QUdpSocket writeDatagram fail. Error: "QAbstractSocket::NetworkError"

[Alexey2016]

I need send big data in short time, but have a problem with QUdpSocket.
Simple test:

#include <QUdpSocket>

void Test_Fail_QUdpSocket(int packet_size)
{
    qDebug() << "Start test, packet_size: " << QString::number(packet_size);
    QUdpSocket socket;
    socket.setSocketOption(QAbstractSocket::SendBufferSizeSocketOption, 10*1024*1024); // is not helped
    qint64 sended_all = 0;
    while(1)
    {
        QByteArray bytes(packet_size, 0xcc);
        //QUdpSocket socket; //if uncomment it - working, but too slow 
        qint64 sended = socket.writeDatagram(bytes, QHostAddress("123.123.123.123"), 50000);
        if( sended<0 )
        {
            qDebug() <<"Err: " << QString::number(socket.error()) << "\tSended: " << QString::number(sended_all);
            //I get error with any "sended_all":  7 - QAbstractSocket::NetworkError
            return;
        }
        socket.flush(); // is not helped
        sended_all += packet_size;
    }
}

int main(int argc, char *argv[])
{
    Test_Fail_QUdpSocket(256);
}

If QHostAddress("127.0.0.1") - then all good with any packet_size <= 8192.
But if host addres is any real host in local network (1Gb) I get error with any packet_size (128,256,512,1024,2048,4096,8192)
and all targets(x86, x64).

But if I use Windows sockets(Winsock2.h) and function "send_to()" then all good!

My: QT 5.5.1, MinGW_492_32, MSVC2013_32, MSVC2013_64.

[VRonin]

you forgot to bind to the port, socket.bind(50000);

[Alexey2016]

@VRonin said in QUdpSocket writeDatagram fail. Error: "QAbstractSocket::NetworkError":

you forgot to bind to the port, socket.bind(50000);

Binds UDP is needed if want to receive.

I think so problem in component, becase it is sends packets long without error if I choose a small package size (<512).
With windows sockets no such problem.