"""TELNET client class.
Based on RFC 854: TELNET Protocol Specification, by J. Postel and
J. Reynolds
Example:
>>> from telnetlib import Telnet
>>> tn = Telnet('www.python.org', 79) # connect to finger port
>>> tn.write('guido\r\n')
>>> print tn.read_all()
Login Name TTY Idle When Where
guido Guido van Rossum pts/2 <Dec 2 11:10> snag.cnri.reston..
>>>
Note that read_all() won't read until eof -- it just reads some data
-- but it guarantees to read at least one byte unless EOF is hit.
It is possible to pass a Telnet object to select.select() in order to
wait until more data is available. Note that in this case,
read_eager() may return '' even if there was data on the socket,
because the protocol negotiation may have eaten the data. This is why
EOFError is needed in some cases to distinguish between "no data" and
"connection closed" (since the socket also appears ready for reading
when it is closed).
Bugs:
- may hang when connection is slow in the middle of an IAC sequence
To do:
- option negotiation
- timeout should be intrinsic to the connection object instead of an
option on one of the read calls only
"""
# Imported modules
import sys
import socket
import select
__all__ = ["Telnet"]
# Tunable parameters
DEBUGLEVEL = 0
# Telnet protocol defaults
TELNET_PORT = 23
# Telnet protocol characters (don't change)
IAC = chr(255) # "Interpret As Command"
DONT = chr(254)
DO = chr(253)
WONT = chr(252)
WILL = chr(251)
theNULL = chr(0)
class Telnet:
"""Telnet interface class.
An instance of this class represents a connection to a telnet
server. The instance is initially not connected; the open()
method must be used to establish a connection. Alternatively, the
host name and optional port number can be passed to the
constructor, too.
Don't try to reopen an already connected instance.
This class has many read_*() methods. Note that some of them
raise EOFError when the end of the connection is read, because
they can return an empty string for other reasons. See the
individual doc strings.
read_until(expected, [timeout])
Read until the expected string has been seen, or a timeout is
hit (default is no timeout); may block.
read_all()
Read all data until EOF; may block.
read_some()
Read at least one byte or EOF; may block.
read_very_eager()
Read all data available already queued or on the socket,
without blocking.
read_eager()
Read either data already queued or some data available on the
socket, without blocking.
read_lazy()
Read all data in the raw queue (processing it first), without
doing any socket I/O.
read_very_lazy()
Reads all data in the cooked queue, without doing any socket
I/O.
"""
def __init__(self, host=None, port=0):
"""Constructor.
When called without arguments, create an unconnected instance.
With a hostname argument, it connects the instance; a port
number is optional.
"""
self.debuglevel = DEBUGLEVEL
self.host = host
self.port = port
self.sock = None
self.rawq = ''
self.irawq = 0
self.cookedq = ''
self.eof = 0
if host:
self.open(host, port)
def open(self, host, port=0):
"""Connect to a host.
The optional second argument is the port number, which
defaults to the standard telnet port (23).
Don't try to reopen an already connected instance.
"""
self.eof = 0
if not port:
port = TELNET_PORT
self.host = host
self.port = port
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.sock.connect((self.host, self.port))
def __del__(self):
"""Destructor -- close the connection."""
self.close()
def msg(self, msg, *args):
"""Print a debug message, when the debug level is > 0.
If extra arguments are present, they are substituted in the
message using the standard string formatting operator.
"""
if self.debuglevel > 0:
print 'Telnet(%s,%d):' % (self.host, self.port),
if args:
print msg % args
else:
print msg
def set_debuglevel(self, debuglevel):
"""Set the debug level.
The higher it is, the more debug output you get (on sys.stdout).
"""
self.debuglevel = debuglevel
def close(self):
"""Close the connection."""
if self.sock:
self.sock.close()
self.sock = 0
self.eof = 1
def get_socket(self):
"""Return the socket object used internally."""
return self.sock
def fileno(self):
"""Return the fileno() of the socket object used internally."""
return self.sock.fileno()
def write(self, buffer):
"""Write a string to the socket, doubling any IAC characters.
Can block if the connection is blocked. May raise
socket.error if the connection is closed.
"""
if IAC in buffer:
buffer = buffer.replace(IAC, IAC+IAC)
self.msg("send %s", `buffer`)
self.sock.sendall(buffer)
def read_until(self, match, timeout=None):
"""Read until a given string is encountered or until timeout.
When no match is found, return whatever is available instead,
possibly the empty string. Raise EOFError if the connection
is closed and no cooked data is available.
"""
n = len(match)
self.process_rawq()
i = self.cookedq.find(match)
if i >= 0:
i = i+n
buf = self.cookedq[:i]
self.cookedq = self.cookedq[i:]
return buf
s_reply = ([self], [], [])
s_args = s_reply
if timeout is not None:
s_args = s_args + (timeout,)
while not self.eof and apply(select.select, s_args) == s_reply:
i = max(0, len(self.cookedq)-n)
self.fill_rawq()
self.process_rawq()
i = self.cookedq.find(match, i)
if i >= 0:
i = i+n
buf = self.cookedq[:i]
self.cookedq = self.cookedq[i:]
return buf
return self.read_very_lazy()
def read_all(self):
"""Read all data until EOF; block until connection closed."""
self.process_rawq()
while not self.eof:
self.fill_rawq()
self.process_rawq()
buf = self.cookedq
self.cookedq = ''
return buf
def read_some(self):
"""Read at least one byte of cooked data unless EOF is hit.
Return '' if EOF is hit. Block if no data is immediately
available.
"""
self.process_rawq()
while not self.cookedq and not self.eof:
self.fill_rawq()
self.process_rawq()
buf = self.cookedq
self.cookedq = ''
return buf
def read_very_eager(self):
"""Read everything that's possible without blocking in I/O (eager).
Raise EOFError if connection closed and no cooked data
available. Return '' if no cooked data available otherwise.
Don't block unless in the midst of an IAC sequence.
"""
self.process_rawq()
while not self.eof and self.sock_avail():
self.fill_rawq()
self.process_rawq()
return self.read_very_lazy()
def read_eager(self):
"""Read readily available data.
Raise EOFError if connection closed and no cooked data
available. Return '' if no cooked data available otherwise.
Don't block unless in the midst of an IAC sequence.
"""
self.process_rawq()
while not self.cookedq and not self.eof and self.sock_avail():
self.fill_rawq()
self.process_rawq()
return self.read_very_lazy()
def read_lazy(self):
"""Process and return data that's already in the queues (lazy).
Raise EOFError if connection closed and no data available.
Return '' if no cooked data available otherwise. Don't block
unless in the midst of an IAC sequence.
"""
self.process_rawq()
return self.read_very_lazy()
def read_very_lazy(self):
"""Return any data available in the cooked queue (very lazy).
Raise EOFError if connection closed and no data available.
Return '' if no cooked data available otherwise. Don't block.
"""
buf = self.cookedq
self.cookedq = ''
if not buf and self.eof and not self.rawq:
raise EOFError, 'telnet connection closed'
return buf
def process_rawq(self):
"""Transfer from raw queue to cooked queue.
Set self.eof when connection is closed. Don't block unless in
the midst of an IAC sequence.
"""
buf = ''
try:
while self.rawq:
c = self.rawq_getchar()
if c == theNULL:
continue
if c == "\021":
continue
if c != IAC:
buf = buf + c
continue
c = self.rawq_getchar()
if c == IAC:
buf = buf + c
elif c in (DO, DONT):
opt = self.rawq_getchar()
self.msg('IAC %s %d', c == DO and 'DO' or 'DONT', ord(c))
self.sock.sendall(IAC + WONT + opt)
elif c in (WILL, WONT):
opt = self.rawq_getchar()
self.msg('IAC %s %d',
c == WILL and 'WILL' or 'WONT', ord(c))
self.sock.sendall(IAC + DONT + opt)
else:
self.msg('IAC %s not recognized' % `c`)
except EOFError: # raised by self.rawq_getchar()
pass
self.cookedq = self.cookedq + buf
def rawq_getchar(self):
"""Get next char from raw queue.
Block if no data is immediately available. Raise EOFError
when connection is closed.
"""
if not self.rawq:
self.fill_rawq()
if self.eof:
raise EOFError
c = self.rawq[self.irawq]
self.irawq = self.irawq + 1
if self.irawq >= len(self.rawq):
self.rawq = ''
self.irawq = 0
return c
def fill_rawq(self):
"""Fill raw queue from exactly one recv() system call.
Block if no data is immediately available. Set self.eof when
connection is closed.
"""
if self.irawq >= len(self.rawq):
self.rawq = ''
self.irawq = 0
# The buffer size should be fairly small so as to avoid quadratic
# behavior in process_rawq() above
buf = self.sock.recv(50)
self.msg("recv %s", `buf`)
self.eof = (not buf)
self.rawq = self.rawq + buf
def sock_avail(self):
"""Test whether data is available on the socket."""
return select.select([self], [], [], 0) == ([self], [], [])
def interact(self):
"""Interaction function, emulates a very dumb telnet client."""
if sys.platform == "win32":
self.mt_interact()
return
while 1:
rfd, wfd, xfd = select.select([self, sys.stdin], [], [])
if self in rfd:
try:
text = self.read_eager()
except EOFError:
print '*** Connection closed by remote host ***'
break
if text:
sys.stdout.write(text)
sys.stdout.flush()
if sys.stdin in rfd:
line = sys.stdin.readline()
if not line:
break
self.write(line)
def mt_interact(self):
"""Multithreaded version of interact()."""
import thread
thread.start_new_thread(self.listener, ())
while 1:
line = sys.stdin.readline()
if not line:
break
self.write(line)
def listener(self):
"""Helper for mt_interact() -- this executes in the other thread."""
while 1:
try:
data = self.read_eager()
except EOFError:
print '*** Connection closed by remote host ***'
return
if data:
sys.stdout.write(data)
else:
sys.stdout.flush()
def expect(self, list, timeout=None):
"""Read until one from a list of a regular expressions matches.
The first argument is a list of regular expressions, either
compiled (re.RegexObject instances) or uncompiled (strings).
The optional second argument is a timeout, in seconds; default
is no timeout.
Return a tuple of three items: the index in the list of the
first regular expression that matches; the match object
returned; and the text read up till and including the match.
If EOF is read and no text was read, raise EOFError.
Otherwise, when nothing matches, return (-1, None, text) where
text is the text received so far (may be the empty string if a
timeout happened).
If a regular expression ends with a greedy match (e.g. '.*')
or if more than one expression can match the same input, the
results are undeterministic, and may depend on the I/O timing.
"""
re = None
list = list[:]
indices = range(len(list))
for i in indices:
if not hasattr(list[i], "search"):
if not re: import re
list[i] = re.compile(list[i])
while 1:
self.process_rawq()
for i in indices:
m = list[i].search(self.cookedq)
if m:
e = m.end()
text = self.cookedq[:e]
self.cookedq = self.cookedq[e:]
return (i, m, text)
if self.eof:
break
if timeout is not None:
r, w, x = select.select([self.fileno()], [], [], timeout)
if not r:
break
self.fill_rawq()
text = self.read_very_lazy()
if not text and self.eof:
raise EOFError
return (-1, None, text)
def test():
"""Test program for telnetlib.
Usage: python telnetlib.py [-d] ... [host [port]]
Default host is localhost; default port is 23.
"""
debuglevel = 0
while sys.argv[1:] and sys.argv[1] == '-d':
debuglevel = debuglevel+1
del sys.argv[1]
host = 'localhost'
if sys.argv[1:]:
host = sys.argv[1]
port = 0
if sys.argv[2:]:
portstr = sys.argv[2]
try:
port = int(portstr)
except ValueError:
port = socket.getservbyname(portstr, 'tcp')
tn = Telnet()
tn.set_debuglevel(debuglevel)
tn.open(host, port)
tn.interact()
tn.close()
if __name__ == '__main__':
test()
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