from socket import socket, AF_INET, SOCK_DGRAM
import sys, random

s = socket(AF_INET, SOCK_DGRAM)

MAX = 65535
PORT = 1060

if 2 <= len(sys.argv) <= 3 and sys.argv[1:] == ['server']:
	host = sys.argv[2] if len(sys.argv) > 2 else ' '
	s.bind((host,PORT))
	print 'Listening at', s.getsockname()
	while 1:
		message, adress = s.recvfrom(MAX)
		if random.randint(0, 1):
			print 'The client at', adress, says, repr(message)
			s.sendto('Your data was %d bytes' % len(message), adress)
		else:
			print 'Pretending to drop package from' adress

elif len(sys.argv) == 3 and sys.argv[1:] == ['client']:
	host = sys.argv[2]
	s.connect((host,PORT)
	print 'Client socket name is ', s.getsockname()
	delay = 0.1
	while 1:
		s.send( 'This is another message' )
		print 'Waiting up to', delay, 'seconds for a reply'
		s.settimeout(delay)
		try:
			data = s.recv(MAX)
		except socket.timeout:
			delay *= 2
			if delay > 2.0:
					raise RuntimeError('I think the server is down')
		except:
			raise
		else:
			break
	print 'The server says' repr(data)

else:
	print >>sys.stderr, 'usage: udp_remote.py server [ <interface> ]'
	print >>sys.stderr, ' or: udp_remote.py client <host>'
	sys.exit(2)