#! /usr/bin/env python

# Minimal interface to the Internet telnet protocol.

#

# It refuses all telnet options and does not recognize any of the other

# telnet commands, but can still be used to connect in line-by-line mode.

# It's also useful to play with a number of other services,

# like time, finger, smtp and even ftp.

#

# Usage: telnet host [port]

#

# The port may be a service name or a decimal port number;

# it defaults to 'telnet'.

import sys, posix, time

from socket import *

BUFSIZE = 1024

# Telnet protocol characters

IAC  = chr(255) # Interpret as command

DONT = chr(254)

DO   = chr(253)

WONT = chr(252)

WILL = chr(251)

def main():

    host = sys.argv[1]

    try:

        hostaddr = gethostbyname(host)

    except error:

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

        sys.exit(2)

    #

    if len(sys.argv) > 2:

        servname = sys.argv[2]

    else:

        servname = 'telnet'

    #

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

        port = eval(servname)

    else:

        try:

            port = getservbyname(servname, 'tcp')

        except error:

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

            sys.exit(2)

    #

    s = socket(AF_INET, SOCK_STREAM)

    #

    try:

        s.connect((host, port))

    except error, msg:

        sys.stderr.write('connect failed: ' + repr(msg) + '\n')

        sys.exit(1)

    #

    pid = posix.fork()

    #

    if pid == 0:

        # child -- read stdin, write socket

        while 1:

            line = sys.stdin.readline()

            s.send(line)

    else:

        # parent -- read socket, write stdout

        iac = 0         # Interpret next char as command

        opt = ''        # Interpret next char as option

        while 1:

            data = s.recv(BUFSIZE)

            if not data:

                # EOF; kill child and exit

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

                posix.kill(pid, 9)

                sys.exit(1)

            cleandata = ''

            for c in data:

                if opt:

                    print ord(c)

                    s.send(opt + c)

                    opt = ''

                elif iac:

                    iac = 0

                    if c == IAC:

                        cleandata = cleandata + c

                    elif c in (DO, DONT):

                        if c == DO: print '(DO)',

                        else: print '(DONT)',

                        opt = IAC + WONT

                    elif c in (WILL, WONT):

                        if c == WILL: print '(WILL)',

                        else: print '(WONT)',

                        opt = IAC + DONT

                    else:

                        print '(command)', ord(c)

                elif c == IAC:

                    iac = 1

                    print '(IAC)',

                else:

                    cleandata = cleandata + c

            sys.stdout.write(cleandata)

            sys.stdout.flush()

try:

    main()

except KeyboardInterrupt:

    pass