[Interest] QUdpSocket, QNetworkDatagram and QNetworkInterface

Nuno Santos nunosantos at imaginando.pt
Tue Oct 29 20:12:37 CET 2019


I’m trying to understand how does Qt decides which QNetworkInterface will be used when a writeDatagram is called.

I’m currently on a system that has both cable and wifi connections available, however, when doing a QUdpSocket writeDatagram the packets are being sent from the wifi adaptor, at least this is what I can infer from the IP address that comes on the packet when it arrives the other machine. What puzzles me is that supposedly, a cable connection is faster than a wifi connection.

While investigating the Qt documentation, it seems that I can use the writeDatagram function of QUdpSocket and specify on the QNetworkDatagram which interface I want to use by using the setInterfaceIndex function.

Is there anyway of knowing which network interface will be used by a QUdpSocket when transmitting data via writeDatagram? Or should I explicitly setInterfaceIndex on QNetworkDatagram and use the writeDatagram QNetworkDatagram variant function in order to have full control?


Best regards,


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