1 #! /usr/bin/env python

     2 

     3 # Client and server for udp (datagram) echo.

     4 #

     5 # Usage: udpecho -s [port]            (to start a server)

     6 # or:    udpecho -c host [port] <file (client)

     7 

     8 import sys

     9 from socket import *

    10 

    11 ECHO_PORT = 50000 + 7

    12 BUFSIZE = 1024

    13 

    14 def main():

    15     if len(sys.argv) < 2:

    16         usage()

    17     if sys.argv[1] == '-s':

    18         server()

    19     elif sys.argv[1] == '-c':

    20         client()

    21     else:

    22         usage()

    23 

    24 def usage():

    25     sys.stdout = sys.stderr

    26     print 'Usage: udpecho -s [port]            (server)'

    27     print 'or:    udpecho -c host [port] <file (client)'

    28     sys.exit(2)

    29 

    30 def server():

    31     if len(sys.argv) > 2:

    32         port = eval(sys.argv[2])

    33     else:

    34         port = ECHO_PORT

    35     s = socket(AF_INET, SOCK_DGRAM)

    36     s.bind(('', port))

    37     print 'udp echo server ready'

    38     while 1:

    39         data, addr = s.recvfrom(BUFSIZE)

    40         print 'server received %r from %r' % (data, addr)

    41         s.sendto(data, addr)

    42 

    43 def client():

    44     if len(sys.argv) < 3:

    45         usage()

    46     host = sys.argv[2]

    47     if len(sys.argv) > 3:

    48         port = eval(sys.argv[3])

    49     else:

    50         port = ECHO_PORT

    51     addr = host, port

    52     s = socket(AF_INET, SOCK_DGRAM)

    53     s.bind(('', 0))

    54     print 'udp echo client ready, reading stdin'

    55     while 1:

    56         line = sys.stdin.readline()

    57         if not line:

    58             break

    59         s.sendto(line, addr)

    60         data, fromaddr = s.recvfrom(BUFSIZE)

    61         print 'client received %r from %r' % (data, fromaddr)

    62 

    63 main()