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#! /usr/bin/env python3
# Client and server for udp (datagram) echo.
#
# Usage: udpecho -s [port] (to start a server)
# or: udpecho -c host [port] <file (client)
import sys
from socket import *
ECHO_PORT = 50000 + 7
BUFSIZE = 1024
def main():
if len(sys.argv) < 2:
usage()
if sys.argv[1] == '-s':
server()
elif sys.argv[1] == '-c':
client()
else:
usage()
def usage():
sys.stdout = sys.stderr
print('Usage: udpecho -s [port] (server)')
print('or: udpecho -c host [port] <file (client)')
sys.exit(2)
def server():
if len(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')
while 1:
data, addr = s.recvfrom(BUFSIZE)
print('server received %r from %r' % (data, addr))
s.sendto(data, addr)
def client():
if len(sys.argv) < 3:
usage()
host = sys.argv[2]
if len(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')
while 1:
line = sys.stdin.readline()
if not line:
break
print('addr = ', addr)
s.sendto(bytes(line, 'ascii'), addr)
data, fromaddr = s.recvfrom(BUFSIZE)
print('client received %r from %r' % (data, fromaddr))
main()
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