Receives and dissect a packet in non-blocking mode.
        Note: on Windows, this won't do anything.

def nonblock_recv(self):
        """Receives and dissect a packet in non-blocking mode.
        Note: on Windows, this won't do anything."""
        self.ins.setnonblock(1)
        p = self.recv(MTU)
        self.ins.setnonblock(0)
        return p