telnet.py without fork()
deckerben
bdeck at lycos.co.uk
Tue Nov 19 15:06:38 EST 2002
Hello.
I need telnet.py to run in a single-tasking environment (i.e. without
posix.fork())for PythonD as a demo of the socketmodule. It seems that
socketmodule runs exactly as it should, but the terminal output is
sometimes a little confusing ... (i.e. CR needs to be pressed more
than normal)
As I still have limited experience with python itself (other than
porting it) and even less with socketmodule, I was hoping for a couple
pointers on how this could run better.
This is a non-forking telnet client for PythonD based on the
socket/telnet.py sample that accompanies the 2.2.1 source
distribution.
begin code:
##########################################################################
#! /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, nt, 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]
sock_bit = chr(66)
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)
# parent -- read socket, write stdout
while 1:
def readsock(sock_bit):
iac = 0 # Interpret next char as command
opt = '' # Interpret next char as option
data = sock_bit + s.recv(BUFSIZE)
# print ord(sock_bit) # for displaying test char
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()
def sendsock():
line = sys.stdin.readline()
s.send(line)
sock_bit = s.recv(2)
if sock_bit != '': readsock(sock_bit)
sendsock()
readsock('\n')
try:
main()
except KeyboardInterrupt:
pass
##############################################################################
As you can see, my biggest problem is finding a routine to smoothly
merge user input with output that is returned from the server. Does
anyone happen to know if there is a definite telnet character(s) that
signal the client terminal that user input is now required?
Is there perhaps a socketmodule function that would serve this
purpose?
Thanks
ben
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