/Doc/library/telnetlib.rst
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- :mod:`telnetlib` --- Telnet client
- ==================================
- .. module:: telnetlib
- :synopsis: Telnet client class.
- .. sectionauthor:: Skip Montanaro <skip@pobox.com>
- .. index:: single: protocol; Telnet
- The :mod:`telnetlib` module provides a :class:`Telnet` class that implements the
- Telnet protocol. See :rfc:`854` for details about the protocol. In addition, it
- provides symbolic constants for the protocol characters (see below), and for the
- telnet options. The symbolic names of the telnet options follow the definitions
- in ``arpa/telnet.h``, with the leading ``TELOPT_`` removed. For symbolic names
- of options which are traditionally not included in ``arpa/telnet.h``, see the
- module source itself.
- The symbolic constants for the telnet commands are: IAC, DONT, DO, WONT, WILL,
- SE (Subnegotiation End), NOP (No Operation), DM (Data Mark), BRK (Break), IP
- (Interrupt process), AO (Abort output), AYT (Are You There), EC (Erase
- Character), EL (Erase Line), GA (Go Ahead), SB (Subnegotiation Begin).
- .. class:: Telnet([host[, port[, timeout]]])
- :class:`Telnet` represents a connection to a Telnet server. The instance is
- initially not connected by default; the :meth:`open` method must be used to
- establish a connection. Alternatively, the host name and optional port
- and timeout can be passed to the constructor, in which case the connection to
- the server will be established before the constructor returns. The optional
- *timeout* parameter specifies a timeout in seconds for the connection attempt (if
- not specified, the global default timeout setting will be used).
- number can be passed to the constructor, to, in which case the connection to
- the server will be established before the constructor returns. The optional
- *timeout* parameter specifies a timeout in seconds for blocking operations
- like the connection attempt (if not specified, or passed as None, the global
- default timeout setting will be used).
- Do not reopen an already connected instance.
- This class has many :meth:`read_\*` methods. Note that some of them raise
- :exc:`EOFError` when the end of the connection is read, because they can return
- an empty string for other reasons. See the individual descriptions below.
- .. versionchanged:: 2.6
- *timeout* was added.
- .. seealso::
- :rfc:`854` - Telnet Protocol Specification
- Definition of the Telnet protocol.
- .. _telnet-objects:
- Telnet Objects
- --------------
- :class:`Telnet` instances have the following methods:
- .. method:: Telnet.read_until(expected[, timeout])
- Read until a given string, *expected*, is encountered or until *timeout* seconds
- have passed.
- When no match is found, return whatever is available instead, possibly the empty
- string. Raise :exc:`EOFError` if the connection is closed and no cooked data is
- available.
- .. method:: Telnet.read_all()
- Read all data until EOF; block until connection closed.
- .. method:: Telnet.read_some()
- Read at least one byte of cooked data unless EOF is hit. Return ``''`` if EOF is
- hit. Block if no data is immediately available.
- .. method:: Telnet.read_very_eager()
- Read everything that can be without blocking in I/O (eager).
- Raise :exc:`EOFError` if connection closed and no cooked data available. Return
- ``''`` if no cooked data available otherwise. Do not block unless in the midst
- of an IAC sequence.
- .. method:: Telnet.read_eager()
- Read readily available data.
- Raise :exc:`EOFError` if connection closed and no cooked data available. Return
- ``''`` if no cooked data available otherwise. Do not block unless in the midst
- of an IAC sequence.
- .. method:: Telnet.read_lazy()
- Process and return data already in the queues (lazy).
- Raise :exc:`EOFError` if connection closed and no data available. Return ``''``
- if no cooked data available otherwise. Do not block unless in the midst of an
- IAC sequence.
- .. method:: Telnet.read_very_lazy()
- Return any data available in the cooked queue (very lazy).
- Raise :exc:`EOFError` if connection closed and no data available. Return ``''``
- if no cooked data available otherwise. This method never blocks.
- .. method:: Telnet.read_sb_data()
- Return the data collected between a SB/SE pair (suboption begin/end). The
- callback should access these data when it was invoked with a ``SE`` command.
- This method never blocks.
- .. versionadded:: 2.3
- .. method:: Telnet.open(host[, port[, timeout]])
- Connect to a host. The optional second argument is the port number, which
- defaults to the standard Telnet port (23). The optional *timeout* parameter
- specifies a timeout in seconds for blocking operations like the connection
- attempt (if not specified, the global default timeout setting will be used).
- Do not try to reopen an already connected instance.
- .. versionchanged:: 2.6
- *timeout* was added.
- .. method:: Telnet.msg(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.
- .. method:: Telnet.set_debuglevel(debuglevel)
- Set the debug level. The higher the value of *debuglevel*, the more debug
- output you get (on ``sys.stdout``).
- .. method:: Telnet.close()
- Close the connection.
- .. method:: Telnet.get_socket()
- Return the socket object used internally.
- .. method:: Telnet.fileno()
- Return the file descriptor of the socket object used internally.
- .. method:: Telnet.write(buffer)
- Write a string to the socket, doubling any IAC characters. This can block if the
- connection is blocked. May raise :exc:`socket.error` if the connection is
- closed.
- .. method:: Telnet.interact()
- Interaction function, emulates a very dumb Telnet client.
- .. method:: Telnet.mt_interact()
- Multithreaded version of :meth:`interact`.
- .. method:: Telnet.expect(list[, timeout])
- Read until one from a list of a regular expressions matches.
- The first argument is a list of regular expressions, either compiled
- (:class:`re.RegexObject` instances) or uncompiled (strings). The optional second
- argument is a timeout, in seconds; the default is to block indefinitely.
- 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 end of file is found and no text was read, raise :exc:`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 (such as ``.*``) or if more
- than one expression can match the same input, the results are indeterministic,
- and may depend on the I/O timing.
- .. method:: Telnet.set_option_negotiation_callback(callback)
- Each time a telnet option is read on the input flow, this *callback* (if set) is
- called with the following parameters : callback(telnet socket, command
- (DO/DONT/WILL/WONT), option). No other action is done afterwards by telnetlib.
- .. _telnet-example:
- Telnet Example
- --------------
- .. sectionauthor:: Peter Funk <pf@artcom-gmbh.de>
- A simple example illustrating typical use::
- import getpass
- import sys
- import telnetlib
- HOST = "localhost"
- user = raw_input("Enter your remote account: ")
- password = getpass.getpass()
- tn = telnetlib.Telnet(HOST)
- tn.read_until("login: ")
- tn.write(user + "\n")
- if password:
- tn.read_until("Password: ")
- tn.write(password + "\n")
- tn.write("ls\n")
- tn.write("exit\n")
- print tn.read_all()