QDataStream and a custom struct

I am trying to serialize a simple discovery packet into a QDataStream.

Packet:

class handshakePacket
{
public:
    quint32 magic_packet;
    quint32 port;
    QString computer_name;
};

Serialization operators overload:

QDataStream &operator<<(QDataStream &out, const handshakePacket &packet)
{
    out << packet.magic_packet << packet.port << packet.computer_name;
    return out;
}
QDataStream &operator>>(QDataStream &in, handshakePacket &packet)
{
    in >> packet.magic_packet >> packet.port >> packet.computer_name;
    return in;
}

Test code:

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QDataStream datastream;
    handshakePacket hpb;
    handshakePacket hpa;

    hpa.magic_packet = 0x12341234;
    hpa.port = 12345;
    hpa.computer_name = QString("hello");
    datastream << hpa;
    datastream >> hpb;

    if(hpb.magic_packet  != hpa.magic_packet) qDebug()<<"fail on magic packet";
    if(hpb.computer_name != hpa.computer_name) qDebug()<<"Fail on computer name";

    return a.exec();
}

"hpb" is always equal to zero and both asserts fail.

I've been trying for a few hours to make this work. I tried to make the handshakePacket class a struct, making it's << and >> overloads friends, making the QDataStream write into a QByteArray, reviewed my overload signatures a few times, making sure the << and the >> are pointing in the right way...

Thanks in advance.

EDIT: Found a solution. I need to rewind the QDataStream:

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QByteArray qba;
    QDataStream datastream(&qba, QIODevice::ReadWrite);
    handshakePacket hpb;
    handshakePacket hpa;

    hpa.magic_packet = 0x12341234;
    hpa.port = 12345;
    hpa.computer_name = QString("hello");
    datastream << hpa;
    datastream.device()->seek(0);
    qDebug() << "atend: "<<datastream.atEnd() ;
    datastream >> hpb;

    if(hpb.magic_packet  != hpa.magic_packet) qDebug()<<"fail on magic packet";
    if(hpb.computer_name != hpa.computer_name) qDebug()<<"Fail on computer name";

    return a.exec();
}

Is there a way to do that without using a QByteArray?