def _udp(src, dst, payload):
 udpHeader = (((_H(src) + _H(dst)) + _H((len(payload) + 8))) + _H(0))
 return (udpHeader + payload)

def _udp ( src , dst , payload ) : udpHeader = ( ( ( _H ( src ) + _H ( dst ) ) + _H ( ( len ( payload ) + 8 ) ) ) + _H ( 0 ) ) return ( udpHeader + payload )
construct a udp datagram with the given source .