udpecho.py

#! /usr/bin/env python

# Client and server for udp (datagram) echo.
#
# Usage: udpecho -s [port] (to start a server)
# or: udpecho -c host [port] <file (client)

importsys
fromsocketimport*

ECHO_PORT=50000+7
BUFSIZE=1024

defmain():
iflen(sys.argv) <2:
usage()
ifsys.argv[1] =='-s':
server()
elifsys.argv[1] =='-c':
client()
else:
usage()

defusage():
sys.stdout=sys.stderr
print'Usage: udpecho -s [port] (server)'
print'or: udpecho -c host [port] <file (client)'
sys.exit(2)

defserver():
iflen(sys.argv) >2:
port=eval(sys.argv[2])
else:
port=ECHO_PORT
s=socket(AF_INET, SOCK_DGRAM)
s.bind(('', port))
print'udp echo server ready'
while1:
data, addr=s.recvfrom(BUFSIZE)
print'server received %r from %r'% (data, addr)
s.sendto(data, addr)

defclient():
iflen(sys.argv) <3:
usage()
host=sys.argv[2]
iflen(sys.argv) >3:
port=eval(sys.argv[3])
else:
port=ECHO_PORT
addr=host, port
s=socket(AF_INET, SOCK_DGRAM)
s.bind(('', 0))
print'udp echo client ready, reading stdin'
while1:
line=sys.stdin.readline()
ifnotline:
break
s.sendto(line, addr)
data, fromaddr=s.recvfrom(BUFSIZE)
print'client received %r from %r'% (data, fromaddr)

main()