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823eb4ba81
telnetlib is unable to connect to a few telnet daemons because of improper IAC handling, heres an attached oneliner to reject WILL messages which will allow many more telnet daemons to work with it, namely FreeBSD.
504 lines
15 KiB
Python
504 lines
15 KiB
Python
"""TELNET client class.
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Based on RFC 854: TELNET Protocol Specification, by J. Postel and
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J. Reynolds
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Example:
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>>> from telnetlib import Telnet
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>>> tn = Telnet('www.python.org', 79) # connect to finger port
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>>> tn.write('guido\r\n')
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>>> print tn.read_all()
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Login Name TTY Idle When Where
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guido Guido van Rossum pts/2 <Dec 2 11:10> snag.cnri.reston..
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>>>
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Note that read_all() won't read until eof -- it just reads some data
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-- but it guarantees to read at least one byte unless EOF is hit.
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It is possible to pass a Telnet object to select.select() in order to
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wait until more data is available. Note that in this case,
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read_eager() may return '' even if there was data on the socket,
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because the protocol negotiation may have eaten the data. This is why
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EOFError is needed in some cases to distinguish between "no data" and
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"connection closed" (since the socket also appears ready for reading
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when it is closed).
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Bugs:
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- may hang when connection is slow in the middle of an IAC sequence
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To do:
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- option negotiation
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- timeout should be intrinsic to the connection object instead of an
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option on one of the read calls only
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"""
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# Imported modules
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import sys
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import socket
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import select
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import string
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# Tunable parameters
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DEBUGLEVEL = 0
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# Telnet protocol defaults
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TELNET_PORT = 23
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# Telnet protocol characters (don't change)
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IAC = chr(255) # "Interpret As Command"
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DONT = chr(254)
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DO = chr(253)
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WONT = chr(252)
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WILL = chr(251)
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theNULL = chr(0)
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class Telnet:
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"""Telnet interface class.
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An instance of this class represents a connection to a telnet
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server. The instance is initially not connected; the open()
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method must be used to establish a connection. Alternatively, the
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host name and optional port number can be passed to the
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constructor, too.
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Don't try to reopen an already connected instance.
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This class has many read_*() methods. Note that some of them
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raise EOFError when the end of the connection is read, because
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they can return an empty string for other reasons. See the
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individual doc strings.
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read_until(expected, [timeout])
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Read until the expected string has been seen, or a timeout is
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hit (default is no timeout); may block.
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read_all()
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Read all data until EOF; may block.
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read_some()
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Read at least one byte or EOF; may block.
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read_very_eager()
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Read all data available already queued or on the socket,
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without blocking.
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read_eager()
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Read either data already queued or some data available on the
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socket, without blocking.
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read_lazy()
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Read all data in the raw queue (processing it first), without
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doing any socket I/O.
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read_very_lazy()
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Reads all data in the cooked queue, without doing any socket
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I/O.
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"""
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def __init__(self, host=None, port=0):
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"""Constructor.
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When called without arguments, create an unconnected instance.
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With a hostname argument, it connects the instance; a port
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number is optional.
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"""
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self.debuglevel = DEBUGLEVEL
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self.host = host
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self.port = port
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self.sock = None
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self.rawq = ''
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self.irawq = 0
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self.cookedq = ''
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self.eof = 0
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if host:
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self.open(host, port)
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def open(self, host, port=0):
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"""Connect to a host.
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The optional second argument is the port number, which
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defaults to the standard telnet port (23).
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Don't try to reopen an already connected instance.
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"""
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self.eof = 0
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if not port:
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port = TELNET_PORT
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self.host = host
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self.port = port
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self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
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self.sock.connect((self.host, self.port))
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def __del__(self):
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"""Destructor -- close the connection."""
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self.close()
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def msg(self, msg, *args):
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"""Print a debug message, when the debug level is > 0.
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If extra arguments are present, they are substituted in the
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message using the standard string formatting operator.
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"""
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if self.debuglevel > 0:
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print 'Telnet(%s,%d):' % (self.host, self.port),
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if args:
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print msg % args
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else:
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print msg
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def set_debuglevel(self, debuglevel):
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"""Set the debug level.
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The higher it is, the more debug output you get (on sys.stdout).
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"""
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self.debuglevel = debuglevel
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def close(self):
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"""Close the connection."""
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if self.sock:
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self.sock.close()
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self.sock = 0
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self.eof = 1
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def get_socket(self):
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"""Return the socket object used internally."""
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return self.sock
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def fileno(self):
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"""Return the fileno() of the socket object used internally."""
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return self.sock.fileno()
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def write(self, buffer):
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"""Write a string to the socket, doubling any IAC characters.
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Can block if the connection is blocked. May raise
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socket.error if the connection is closed.
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"""
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if IAC in buffer:
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buffer = string.replace(buffer, IAC, IAC+IAC)
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self.msg("send %s", `buffer`)
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self.sock.send(buffer)
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def read_until(self, match, timeout=None):
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"""Read until a given string is encountered or until timeout.
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When no match is found, return whatever is available instead,
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possibly the empty string. Raise EOFError if the connection
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is closed and no cooked data is available.
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"""
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n = len(match)
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self.process_rawq()
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i = string.find(self.cookedq, match)
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if i >= 0:
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i = i+n
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buf = self.cookedq[:i]
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self.cookedq = self.cookedq[i:]
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return buf
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s_reply = ([self], [], [])
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s_args = s_reply
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if timeout is not None:
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s_args = s_args + (timeout,)
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while not self.eof and apply(select.select, s_args) == s_reply:
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i = max(0, len(self.cookedq)-n)
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self.fill_rawq()
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self.process_rawq()
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i = string.find(self.cookedq, match, i)
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if i >= 0:
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i = i+n
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buf = self.cookedq[:i]
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self.cookedq = self.cookedq[i:]
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return buf
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return self.read_very_lazy()
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def read_all(self):
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"""Read all data until EOF; block until connection closed."""
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self.process_rawq()
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while not self.eof:
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self.fill_rawq()
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self.process_rawq()
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buf = self.cookedq
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self.cookedq = ''
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return buf
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def read_some(self):
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"""Read at least one byte of cooked data unless EOF is hit.
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Return '' if EOF is hit. Block if no data is immediately
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available.
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"""
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self.process_rawq()
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while not self.cookedq and not self.eof:
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self.fill_rawq()
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self.process_rawq()
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buf = self.cookedq
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self.cookedq = ''
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return buf
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def read_very_eager(self):
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"""Read everything that's possible without blocking in I/O (eager).
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Raise EOFError if connection closed and no cooked data
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available. Return '' if no cooked data available otherwise.
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Don't block unless in the midst of an IAC sequence.
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"""
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self.process_rawq()
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while not self.eof and self.sock_avail():
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self.fill_rawq()
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self.process_rawq()
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return self.read_very_lazy()
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def read_eager(self):
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"""Read readily available data.
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Raise EOFError if connection closed and no cooked data
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available. Return '' if no cooked data available otherwise.
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Don't block unless in the midst of an IAC sequence.
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"""
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self.process_rawq()
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while not self.cookedq and not self.eof and self.sock_avail():
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self.fill_rawq()
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self.process_rawq()
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return self.read_very_lazy()
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def read_lazy(self):
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"""Process and return data that's already in the queues (lazy).
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Raise EOFError if connection closed and no data available.
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Return '' if no cooked data available otherwise. Don't block
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unless in the midst of an IAC sequence.
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"""
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self.process_rawq()
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return self.read_very_lazy()
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def read_very_lazy(self):
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"""Return any data available in the cooked queue (very lazy).
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Raise EOFError if connection closed and no data available.
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Return '' if no cooked data available otherwise. Don't block.
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"""
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buf = self.cookedq
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self.cookedq = ''
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if not buf and self.eof and not self.rawq:
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raise EOFError, 'telnet connection closed'
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return buf
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def process_rawq(self):
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"""Transfer from raw queue to cooked queue.
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Set self.eof when connection is closed. Don't block unless in
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the midst of an IAC sequence.
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"""
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buf = ''
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try:
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while self.rawq:
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c = self.rawq_getchar()
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if c == theNULL:
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continue
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if c == "\021":
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continue
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if c != IAC:
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buf = buf + c
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continue
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c = self.rawq_getchar()
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if c == IAC:
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buf = buf + c
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elif c in (DO, DONT):
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opt = self.rawq_getchar()
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self.msg('IAC %s %d', c == DO and 'DO' or 'DONT', ord(c))
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self.sock.send(IAC + WONT + opt)
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elif c in (WILL, WONT):
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opt = self.rawq_getchar()
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self.msg('IAC %s %d',
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c == WILL and 'WILL' or 'WONT', ord(c))
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self.sock.send(IAC + DONT + opt)
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else:
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self.msg('IAC %s not recognized' % `c`)
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except EOFError: # raised by self.rawq_getchar()
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pass
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self.cookedq = self.cookedq + buf
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def rawq_getchar(self):
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"""Get next char from raw queue.
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Block if no data is immediately available. Raise EOFError
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when connection is closed.
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"""
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if not self.rawq:
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self.fill_rawq()
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if self.eof:
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raise EOFError
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c = self.rawq[self.irawq]
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self.irawq = self.irawq + 1
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if self.irawq >= len(self.rawq):
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self.rawq = ''
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self.irawq = 0
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return c
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def fill_rawq(self):
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"""Fill raw queue from exactly one recv() system call.
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Block if no data is immediately available. Set self.eof when
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connection is closed.
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"""
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if self.irawq >= len(self.rawq):
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self.rawq = ''
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self.irawq = 0
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# The buffer size should be fairly small so as to avoid quadratic
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# behavior in process_rawq() above
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buf = self.sock.recv(50)
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self.msg("recv %s", `buf`)
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self.eof = (not buf)
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self.rawq = self.rawq + buf
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def sock_avail(self):
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"""Test whether data is available on the socket."""
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return select.select([self], [], [], 0) == ([self], [], [])
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def interact(self):
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"""Interaction function, emulates a very dumb telnet client."""
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if sys.platform == "win32":
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self.mt_interact()
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return
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while 1:
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rfd, wfd, xfd = select.select([self, sys.stdin], [], [])
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if self in rfd:
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try:
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text = self.read_eager()
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except EOFError:
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print '*** Connection closed by remote host ***'
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break
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if text:
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sys.stdout.write(text)
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sys.stdout.flush()
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if sys.stdin in rfd:
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line = sys.stdin.readline()
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if not line:
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break
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self.write(line)
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def mt_interact(self):
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"""Multithreaded version of interact()."""
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import thread
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thread.start_new_thread(self.listener, ())
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while 1:
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line = sys.stdin.readline()
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if not line:
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break
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self.write(line)
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def listener(self):
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"""Helper for mt_interact() -- this executes in the other thread."""
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while 1:
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try:
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data = self.read_eager()
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except EOFError:
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print '*** Connection closed by remote host ***'
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return
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if data:
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sys.stdout.write(data)
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else:
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sys.stdout.flush()
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def expect(self, list, timeout=None):
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"""Read until one from a list of a regular expressions matches.
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The first argument is a list of regular expressions, either
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compiled (re.RegexObject instances) or uncompiled (strings).
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The optional second argument is a timeout, in seconds; default
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is no timeout.
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Return a tuple of three items: the index in the list of the
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first regular expression that matches; the match object
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returned; and the text read up till and including the match.
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If EOF is read and no text was read, raise EOFError.
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Otherwise, when nothing matches, return (-1, None, text) where
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text is the text received so far (may be the empty string if a
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timeout happened).
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If a regular expression ends with a greedy match (e.g. '.*')
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or if more than one expression can match the same input, the
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results are undeterministic, and may depend on the I/O timing.
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"""
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re = None
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list = list[:]
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indices = range(len(list))
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for i in indices:
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if not hasattr(list[i], "search"):
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if not re: import re
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list[i] = re.compile(list[i])
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while 1:
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self.process_rawq()
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for i in indices:
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m = list[i].search(self.cookedq)
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if m:
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e = m.end()
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text = self.cookedq[:e]
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self.cookedq = self.cookedq[e:]
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return (i, m, text)
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if self.eof:
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break
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if timeout is not None:
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r, w, x = select.select([self.fileno()], [], [], timeout)
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if not r:
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break
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self.fill_rawq()
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text = self.read_very_lazy()
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if not text and self.eof:
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raise EOFError
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return (-1, None, text)
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def test():
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"""Test program for telnetlib.
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Usage: python telnetlib.py [-d] ... [host [port]]
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Default host is localhost; default port is 23.
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"""
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debuglevel = 0
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while sys.argv[1:] and sys.argv[1] == '-d':
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debuglevel = debuglevel+1
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del sys.argv[1]
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host = 'localhost'
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if sys.argv[1:]:
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host = sys.argv[1]
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port = 0
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if sys.argv[2:]:
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portstr = sys.argv[2]
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try:
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port = int(portstr)
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except ValueError:
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port = socket.getservbyname(portstr, 'tcp')
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tn = Telnet()
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tn.set_debuglevel(debuglevel)
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tn.open(host, port)
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tn.interact()
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tn.close()
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if __name__ == '__main__':
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test()
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