udp_remote.py

#!/usr/bin/env python


import random
import socket
import sys
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

MAX = 65535
PORT = 1060

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

elif len(sys.argv) == 3 and sys.argv[1] == 'client':
    hostname = sys.argv[2]
    s.connect((hostname, PORT))
    print 'Client socket name is', s.getsockname()
    delay = 0.1
    while True:
        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  # wait even longer for the next request
            if delay > 2.0:
                raise RuntimeError('I think the server is down')
        except:
            raise   # a real error, so we let the user see it
        else:
            break   # we are done, and can stop looping

    print 'The server says', repr(data)

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