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
  16 import sys, posix, time
  17 from socket import *
  18
  19 BUFSIZE = 1024
  20
  21 # Telnet protocol characters
  22
  23 IAC  = chr(255) # Interpret as command
  24 DONT = chr(254)
  25 DO   = chr(253)
  26 WONT = chr(252)
  27 WILL = chr(251)
  28
  29 def 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
 106 try:
 107     main()
 108 except KeyboardInterrupt:
 109     pass