tcp_deadlock.py

#!/usr/bin/env python

# TCP client and server that leave
# too much data waiting. From Foundations

import socket
import sys

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

HOST = '127.0.0.1'
PORT = 1060

if sys.argv[1:] == ['server']:
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.bind((HOST, PORT))
    s.listen(1)
    while True:
        print 'Listening at', s.getsockname()
        sc, sockname = s.accept()
        print 'Processing up to 1024 bytes at a time from', sockname
        n = 0
        while True:
            message = sc.recv(1024)
            if not message:
                break
            sc.sendall(message.upper())
            n += len(message)
            print '\r%d bytes processed so far' % (n,),
            sys.stdout.flush()
        print
        sc.close()
        print 'Completed processing'

elif len(sys.argv) == 3 and sys.argv[1] == 'client' and sys.argv[2].isdigit():
    bytes = (int(sys.argv[2]) + 15) // 16 * 16
    message = 'capitalize this!'
    print 'Sending', bytes, 'bytes if data, in chunks of 16 bytes'
    s.connect((HOST, PORT))
    sent = 0
    while sent < bytes:
        s.sendall(message)
        sent += len(message)
        print '\r%d bytes sent' % (sent,),
        sys.stdout.flush()

    print
    s.shutdown(socket.SHUT_WR)
    print 'Receiving all the data the server sends back'
    received = 0
    while True:
        data = s.recv(42)
        if not received:
            print 'The first data received says', repr(data)
        received += len(data)
        if not data:
            break
        print '\r%d bytes received' % (received,),
    s.close()

else:
    print >>sys.stderr, 'usage: tcp_deadlock.py server | client <bytes>'