What are legal addresses for binding a QUdpSocket?

Question

I tried to bind my socket to some random address 10.1.1.1:12001, and got QAbstractSocket::SocketAddressNotAvailableError. Than i wrote a simple code:

for (int i = 0; i < 256; i++) {
    QHostAddress address0(QString::number(i) + ".0.0.1");
    quint16 port = 12101;
    QUdpSocket* m_socket = new QUdpSocket();
    if (m_socket->bind(address0, port, QUdpSocket::ShareAddress | QUdpSocket::ReuseAddressHint)) {
        qDebug() << i;
    }
}

Only to learn that IP must start with 127 or 224-239. So it must be Class D address.. But I just didn't find anything in the qt documentation.

Is it a normal behaviour? Is there a possibility to use a global net IP for binding? Or at least use 192.168.x.x as IP of another computer in LAN?

Answer 1

You are not allowed to bind the socket to an arbitrary network IP address. You can only do it with an IP address of one of your network devices or some special IP addresses like 0.0.0.0. By default you always have the 127.0.0.1 but surely you have another network address in your computer.

By the other way if you want to write/read some data over an UDP Socket It's not necessary to bind it to a network address, you can use writeDatagram() or readDatagram() methods of the QUdpSocket class