/Demo/sockets/telnet.py

  1#! /usr/bin/env python
  2
  3# Minimal interface to the Internet telnet protocol.
  4#
  5# It refuses all telnet options and does not recognize any of the other
  6# telnet commands, but can still be used to connect in line-by-line mode.
  7# It's also useful to play with a number of other services,
  8# like time, finger, smtp and even ftp.
  9#
 10# Usage: telnet host [port]
 11#
 12# The port may be a service name or a decimal port number;
 13# it defaults to 'telnet'.
 14
 15
 16import sys, posix, time
 17from socket import *
 18
 19BUFSIZE = 1024
 20
 21# Telnet protocol characters
 22
 23IAC  = chr(255) # Interpret as command
 24DONT = chr(254)
 25DO   = chr(253)
 26WONT = chr(252)
 27WILL = chr(251)
 28
 29def main():
 30    host = sys.argv[1]
 31    try:
 32        hostaddr = gethostbyname(host)
 33    except error:
 34        sys.stderr.write(sys.argv[1] + ': bad host name\n')
 35        sys.exit(2)
 36    #
 37    if len(sys.argv) > 2:
 38        servname = sys.argv[2]
 39    else:
 40        servname = 'telnet'
 41    #
 42    if '0' <= servname[:1] <= '9':
 43        port = eval(servname)
 44    else:
 45        try:
 46            port = getservbyname(servname, 'tcp')
 47        except error:
 48            sys.stderr.write(servname + ': bad tcp service name\n')
 49            sys.exit(2)
 50    #
 51    s = socket(AF_INET, SOCK_STREAM)
 52    #
 53    try:
 54        s.connect((host, port))
 55    except error, msg:
 56        sys.stderr.write('connect failed: ' + repr(msg) + '\n')
 57        sys.exit(1)
 58    #
 59    pid = posix.fork()
 60    #
 61    if pid == 0:
 62        # child -- read stdin, write socket
 63        while 1:
 64            line = sys.stdin.readline()
 65            s.send(line)
 66    else:
 67        # parent -- read socket, write stdout
 68        iac = 0         # Interpret next char as command
 69        opt = ''        # Interpret next char as option
 70        while 1:
 71            data = s.recv(BUFSIZE)
 72            if not data:
 73                # EOF; kill child and exit
 74                sys.stderr.write( '(Closed by remote host)\n')
 75                posix.kill(pid, 9)
 76                sys.exit(1)
 77            cleandata = ''
 78            for c in data:
 79                if opt:
 80                    print ord(c)
 81                    s.send(opt + c)
 82                    opt = ''
 83                elif iac:
 84                    iac = 0
 85                    if c == IAC:
 86                        cleandata = cleandata + c
 87                    elif c in (DO, DONT):
 88                        if c == DO: print '(DO)',
 89                        else: print '(DONT)',
 90                        opt = IAC + WONT
 91                    elif c in (WILL, WONT):
 92                        if c == WILL: print '(WILL)',
 93                        else: print '(WONT)',
 94                        opt = IAC + DONT
 95                    else:
 96                        print '(command)', ord(c)
 97                elif c == IAC:
 98                    iac = 1
 99                    print '(IAC)',
100                else:
101                    cleandata = cleandata + c
102            sys.stdout.write(cleandata)
103            sys.stdout.flush()
104
105
106try:
107    main()
108except KeyboardInterrupt:
109    pass