def parser(self):
        """
        Get a function for parsing a datagram read from a I{tun} device.

        @return: A function which accepts a datagram exactly as might be read
            from a I{tun} device.  The datagram is expected to ultimately carry
            a UDP datagram.  When called, it returns a L{list} of L{tuple}s.
            Each tuple has the UDP application data as the first element and
            the sender address as the second element.
        """
        datagrams = []
        receiver = DatagramProtocol()

        def capture(*args):
            datagrams.append(args)

        receiver.datagramReceived = capture

        udp = RawUDPProtocol()
        udp.addProto(12345, receiver)

        ip = IPProtocol()
        ip.addProto(17, udp)

        def parse(data):
            # TUN devices omit the ethernet framing so we can start parsing
            # right at the IP layer.
            ip.datagramReceived(data, False, None, None, None)
            return datagrams

        return parse

        Get a function for parsing a datagram read from a I{tun} device.

        @return: A function which accepts a datagram exactly as might be read
            from a I{tun} device.  The datagram is expected to ultimately carry
            a UDP datagram.  When called, it returns a L{list} of L{tuple}s.
            Each tuple has the UDP application data as the first element and
            the sender address as the second element.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/pair/test/test_tuntap.py