ping.py

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.sendto('PING', ('127.0.0.1',540))

data, addr = s.recvfrom(1024)
print data, addr

pongd.py

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind(('0.0.0.0', 540))

print "Socket ready"
while True:
    data, addr = s.recvfrom(1024)
    print "Received presumed ping from ",addr
    s.sendto('PONG', addr)
    print "Sent pong"