Calling QTcpSocket::bind() before connectToHost() does not bind the address of the outgoing connection actually.

Qt 5 and QTBUG-121 introduced a new API to bind the local address for QTcpSocket. However, it does not work actually, the socket always use default local address to connect.
The cause is QAbstractSocketPrivate::_q_connectToNextAddress() calls initSocketLayer(), which close the bound socket, replace it with a newly created socket, and leave the new socket unbound.