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() 64
