Demo/threads/telnet.py

# Minimal interface to the Internet telnet protocol.
#
# *** modified to use threads ***
#
# 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, os, time
from socket import *
import thread

BUFSIZE = 8*1024

# Telnet protocol characters

IAC  = chr(255)	# Interpret as command
DONT = chr(254)
DO   = chr(253)
WONT = chr(252)
WILL = chr(251)

def main():
	if len(sys.argv) != 2:
		sys.stderr.write('usage: telnet hostname\n')
		sys.exit(2)
	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: ' + `msg` + '\n')
		sys.exit(1)
	#
	thread.start_new(child, (s,))
	parent(s)

def parent(s):
	# read socket, write stdout
	iac = 0		# Interpret next char as command
	opt = ''	# Interpret next char as option
	while 1:
		data, dummy = s.recvfrom(BUFSIZE)
		if not data:
			# EOF -- exit
			sys.stderr.write( '(Closed by remote host)\n')
			sys.exit(1)
		cleandata = ''
		for c in data:
			if opt:
				print ord(c)
##				print '(replying: ' + `opt+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()
##		print 'Out:', `cleandata`

def child(s):
	# read stdin, write socket
	while 1:
		line = sys.stdin.readline()
##		print 'Got:', `line`
		if not line: break
		s.send(line)

main()