1 # Minimal interface to the Internet telnet protocol.

     2 #

     3 # *** modified to use threads ***

     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, os, time

    17 from socket import *

    18 import thread

    19 

    20 BUFSIZE = 8*1024

    21 

    22 # Telnet protocol characters

    23 

    24 IAC  = chr(255) # Interpret as command

    25 DONT = chr(254)

    26 DO   = chr(253)

    27 WONT = chr(252)

    28 WILL = chr(251)

    29 

    30 def main():

    31     if len(sys.argv) < 2:

    32         sys.stderr.write('usage: telnet hostname [port]\n')

    33         sys.exit(2)

    34     host = sys.argv[1]

    35     try:

    36         hostaddr = gethostbyname(host)

    37     except error:

    38         sys.stderr.write(sys.argv[1] + ': bad host name\n')

    39         sys.exit(2)

    40     #

    41     if len(sys.argv) > 2:

    42         servname = sys.argv[2]

    43     else:

    44         servname = 'telnet'

    45     #

    46     if '0' <= servname[:1] <= '9':

    47         port = eval(servname)

    48     else:

    49         try:

    50             port = getservbyname(servname, 'tcp')

    51         except error:

    52             sys.stderr.write(servname + ': bad tcp service name\n')

    53             sys.exit(2)

    54     #

    55     s = socket(AF_INET, SOCK_STREAM)

    56     #

    57     try:

    58         s.connect((host, port))

    59     except error, msg:

    60         sys.stderr.write('connect failed: %r\n' % (msg,))

    61         sys.exit(1)

    62     #

    63     thread.start_new(child, (s,))

    64     parent(s)

    65 

    66 def parent(s):

    67     # read socket, write stdout

    68     iac = 0         # Interpret next char as command

    69     opt = ''        # Interpret next char as option

    70     while 1:

    71         data, dummy = s.recvfrom(BUFSIZE)

    72         if not data:

    73             # EOF -- exit

    74             sys.stderr.write( '(Closed by remote host)\n')

    75             sys.exit(1)

    76         cleandata = ''

    77         for c in data:

    78             if opt:

    79                 print ord(c)

    80 ##                              print '(replying: %r)' % (opt+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 ##              print 'Out:', repr(cleandata)

   105 

   106 def child(s):

   107     # read stdin, write socket

   108     while 1:

   109         line = sys.stdin.readline()

   110 ##              print 'Got:', repr(line)

   111         if not line: break

   112         s.send(line)

   113 

   114 main()