2 :mod:`telnetlib` --- Telnet client
3 ==================================
6 :synopsis: Telnet client class.
7 .. sectionauthor:: Skip Montanaro <skip@pobox.com>
10 .. index:: single: protocol; Telnet
12 The :mod:`telnetlib` module provides a :class:`Telnet` class that implements the
13 Telnet protocol. See :rfc:`854` for details about the protocol. In addition, it
14 provides symbolic constants for the protocol characters (see below), and for the
15 telnet options. The symbolic names of the telnet options follow the definitions
16 in ``arpa/telnet.h``, with the leading ``TELOPT_`` removed. For symbolic names
17 of options which are traditionally not included in ``arpa/telnet.h``, see the
20 The symbolic constants for the telnet commands are: IAC, DONT, DO, WONT, WILL,
21 SE (Subnegotiation End), NOP (No Operation), DM (Data Mark), BRK (Break), IP
22 (Interrupt process), AO (Abort output), AYT (Are You There), EC (Erase
23 Character), EL (Erase Line), GA (Go Ahead), SB (Subnegotiation Begin).
26 .. class:: Telnet([host[, port[, timeout]]])
28 :class:`Telnet` represents a connection to a Telnet server. The instance is
29 initially not connected by default; the :meth:`open` method must be used to
30 establish a connection. Alternatively, the host name and optional port
31 and timeout can be passed to the constructor, in which case the connection to
32 the server will be established before the constructor returns. The optional
33 *timeout* parameter specifies a timeout in seconds for the connection attempt (if
34 not specified, the global default timeout setting will be used).
36 number can be passed to the constructor, to, in which case the connection to
37 the server will be established before the constructor returns. The optional
38 *timeout* parameter specifies a timeout in seconds for blocking operations
39 like the connection attempt (if not specified, or passed as None, the global
40 default timeout setting will be used).
42 Do not reopen an already connected instance.
44 This class has many :meth:`read_\*` methods. Note that some of them raise
45 :exc:`EOFError` when the end of the connection is read, because they can return
46 an empty string for other reasons. See the individual descriptions below.
48 .. versionchanged:: 2.6
54 :rfc:`854` - Telnet Protocol Specification
55 Definition of the Telnet protocol.
63 :class:`Telnet` instances have the following methods:
66 .. method:: Telnet.read_until(expected[, timeout])
68 Read until a given string, *expected*, is encountered or until *timeout* seconds
71 When no match is found, return whatever is available instead, possibly the empty
72 string. Raise :exc:`EOFError` if the connection is closed and no cooked data is
76 .. method:: Telnet.read_all()
78 Read all data until EOF; block until connection closed.
81 .. method:: Telnet.read_some()
83 Read at least one byte of cooked data unless EOF is hit. Return ``''`` if EOF is
84 hit. Block if no data is immediately available.
87 .. method:: Telnet.read_very_eager()
89 Read everything that can be without blocking in I/O (eager).
91 Raise :exc:`EOFError` if connection closed and no cooked data available. Return
92 ``''`` if no cooked data available otherwise. Do not block unless in the midst
96 .. method:: Telnet.read_eager()
98 Read readily available data.
100 Raise :exc:`EOFError` if connection closed and no cooked data available. Return
101 ``''`` if no cooked data available otherwise. Do not block unless in the midst
105 .. method:: Telnet.read_lazy()
107 Process and return data already in the queues (lazy).
109 Raise :exc:`EOFError` if connection closed and no data available. Return ``''``
110 if no cooked data available otherwise. Do not block unless in the midst of an
114 .. method:: Telnet.read_very_lazy()
116 Return any data available in the cooked queue (very lazy).
118 Raise :exc:`EOFError` if connection closed and no data available. Return ``''``
119 if no cooked data available otherwise. This method never blocks.
122 .. method:: Telnet.read_sb_data()
124 Return the data collected between a SB/SE pair (suboption begin/end). The
125 callback should access these data when it was invoked with a ``SE`` command.
126 This method never blocks.
128 .. versionadded:: 2.3
131 .. method:: Telnet.open(host[, port[, timeout]])
133 Connect to a host. The optional second argument is the port number, which
134 defaults to the standard Telnet port (23). The optional *timeout* parameter
135 specifies a timeout in seconds for blocking operations like the connection
136 attempt (if not specified, the global default timeout setting will be used).
138 Do not try to reopen an already connected instance.
140 .. versionchanged:: 2.6
144 .. method:: Telnet.msg(msg[, *args])
146 Print a debug message when the debug level is ``>`` 0. If extra arguments are
147 present, they are substituted in the message using the standard string
151 .. method:: Telnet.set_debuglevel(debuglevel)
153 Set the debug level. The higher the value of *debuglevel*, the more debug
154 output you get (on ``sys.stdout``).
157 .. method:: Telnet.close()
159 Close the connection.
162 .. method:: Telnet.get_socket()
164 Return the socket object used internally.
167 .. method:: Telnet.fileno()
169 Return the file descriptor of the socket object used internally.
172 .. method:: Telnet.write(buffer)
174 Write a string to the socket, doubling any IAC characters. This can block if the
175 connection is blocked. May raise :exc:`socket.error` if the connection is
179 .. method:: Telnet.interact()
181 Interaction function, emulates a very dumb Telnet client.
184 .. method:: Telnet.mt_interact()
186 Multithreaded version of :meth:`interact`.
189 .. method:: Telnet.expect(list[, timeout])
191 Read until one from a list of a regular expressions matches.
193 The first argument is a list of regular expressions, either compiled
194 (:class:`re.RegexObject` instances) or uncompiled (strings). The optional second
195 argument is a timeout, in seconds; the default is to block indefinitely.
197 Return a tuple of three items: the index in the list of the first regular
198 expression that matches; the match object returned; and the text read up till
199 and including the match.
201 If end of file is found and no text was read, raise :exc:`EOFError`. Otherwise,
202 when nothing matches, return ``(-1, None, text)`` where *text* is the text
203 received so far (may be the empty string if a timeout happened).
205 If a regular expression ends with a greedy match (such as ``.*``) or if more
206 than one expression can match the same input, the results are indeterministic,
207 and may depend on the I/O timing.
210 .. method:: Telnet.set_option_negotiation_callback(callback)
212 Each time a telnet option is read on the input flow, this *callback* (if set) is
213 called with the following parameters : callback(telnet socket, command
214 (DO/DONT/WILL/WONT), option). No other action is done afterwards by telnetlib.
222 .. sectionauthor:: Peter Funk <pf@artcom-gmbh.de>
225 A simple example illustrating typical use::
232 user = raw_input("Enter your remote account: ")
233 password = getpass.getpass()
235 tn = telnetlib.Telnet(HOST)
237 tn.read_until("login: ")
238 tn.write(user + "\n")
240 tn.read_until("Password: ")
241 tn.write(password + "\n")