QPixmap over QUdpSocket - can't read correct data

Question

I'm using Qt5 and i'm trying to send QPixmap over QUdpProtocol with QByteArray packet in QDataStream. Send pixmap is simple (and correct?):

QByteArray block;
QDataStream out(&block, QIODevice::WriteOnly);

out.setVersion(QDataStream::Qt_5_0);
out << (quint32)0;
out << pixmap;
out.device()->seek(0);
out << (quint32)(block.size() - sizeof(quint32));

socket->write(block);
qDebug() << "Block size:" << (float)(block.size()/1024.f) << "KB";

But reading... Nothing happens - I mean, QLabel isn't filled, any change, any error message.

QByteArray buffer;
buffer.resize(sock->pendingDatagramSize());
sock->readDatagram(buffer.data(), buffer.size(), &remoteAddr, &remotePort);

if (sock->bytesAvailable() > 0)
    return;

QDataStream out(&buffer, QIODevice::ReadOnly);
out.setVersion(QDataStream::Qt_5_0);

QPixmap p;
//out.device()->seek(0);
out >> p;
ui->label->setPixmap(p);

I know about packet fragmentation in UDP, but I tried sending 50 pixels, 20, 10, 5, and finally - 1. Nothing. Both programs shows same bytes count (sended and received). If this matters, I'm binded both sockets at QHostAddress::LocalHost with same port, but raw text was sended successfully.

What I am doing wrong?

Answer 1

Huh, success.
Code from internet is invalid . I tried this way:

QByteArray frame;

QDataStream out(&frame, QIODevice::WriteOnly);
out << myPixmap;

QDataStream in(&frame, QIODevice::ReadOnly);
QPixmap pix2;
in >> pix2;
ui->label->setPixmap(pix2);

It works and it's easy.

On Qt5 bytes in start about size isn't needed. Also, transfer by TCP/UDP works fine (if you have troubles, remember about maximum packet size).