Exscript.protocols.telnetlib module

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
')
>>> 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

class Exscript.protocols.telnetlib.Telnet(host=None, port=0, encoding='latin1', **kwargs)

Bases: future.types.newobject.newobject

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_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.

__init__(host=None, port=0, encoding='latin1', **kwargs)

Constructor.

When called without arguments, create an unconnected instance. With a hostname argument, it connects the instance; a port number is optional.

close()

Close the connection.

expect(relist, timeout=None, cleanup=None)

Like waitfor(), but removes the matched data from the incoming buffer.

fileno()

Return the fileno() of the socket object used internally.

fill_rawq()

Fill raw queue from exactly one recv() system call.

Block if no data is immediately available. Set self.eof when connection is closed.

get_socket()

Return the socket object used internally.

interact()

Interaction function, emulates a very dumb telnet client.

listener()

Helper for mt_interact() – this executes in the other thread.

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.

mt_interact()

Multithreaded version of interact().

open(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.

process_rawq()

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.

rawq_getchar()

Get next char from raw queue.

Block if no data is immediately available. Raise EOFError when connection is closed.

read_all()

Read all data until EOF; block until connection closed.

read_eager()

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.

read_lazy()

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.

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.

read_very_eager()

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.

read_very_lazy()

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.

set_debuglevel(debuglevel)

Set the debug level.

The higher it is, the more debug output you get (on stdout).

set_receive_callback(callback, *args, **kwargs)

The callback function called after each receipt of any data.

set_window_size(rows, cols)

Change the size of the terminal window, if the remote end supports NAWS. If it doesn’t, the method returns silently.

sock_avail()

Test whether data is available on the socket.

waitfor(relist, timeout=None, cleanup=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.

write(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.