asynctelnet 0.2.5

Python 3 anyio Telnet server and client Protocol library

Introduction

asynctelnet is an asynchronous Telnet Client and Server library for python. This project requires python 3.6 and later, using the anyio module.

asynctelnet is a heavily modified anyio-ization of the telnetlib3 module.

Quick Example

Authoring a Telnet Server using Streams interface that offers a basic war game:

import anyio, asynctelnet

async def shell(tcp):
    async with asynctelnet.TelnetServer(tcp) as stream:
        # this will fail if no charset has been negotiated
        await stream.send('\r\nWould you like to play a game? ')
        inp = await reader.receive(1)
        if inp:
            await stream.echo(inp)
            await stream.send('\r\nThey say the only way to win '
                              'is to not play at all.\r\n')

async def main():
    listener = await anyio.create_tcp_listener(local_port=56023)
    await listener.serve(shell)
anyio.run(main)

Authoring a Telnet Client that plays the war game with this server:

import anyio, asynctelnet

async def shell(tcp):
    async with asynctelnet.TelnetClient(tcp, client=True) as stream:
        while True:
            # read stream until '?' mark is found
            outp = await stream.receive(1024)
            if not outp:
                # End of File
                break
            elif '?' in outp:
                # reply all questions with 'y'.
                await stream.send('y')

            # display all server output
            print(outp, flush=True)

    # EOF
    print()

async def main():
    async with await connect_tcp('localhost', 56023) as client:
        await shell(client)
anyio.run(main)

Command Line

Two command line scripts are distributed with this package.

asynctelnet-client

Small terminal telnet client. Some example destinations and options:

asynctelnet-client nethack.alt.org
asynctelnet-client --encoding=cp437 --force-binary blackflag.acid.org
asynctelnet-client htc.zapto.org

asynctelnet-server

Telnet server providing the default debugging shell. This provides a simple shell server that allows introspection of the session’s values, for example:

tel:sh> help
quit, writer, slc, toggle [option|all], reader, proto

tel:sh> writer
<TelnetWriter server mode:kludge +lineflow -xon_any +slc_sim server-will:BINARY,ECHO,SGA client-will:BINARY,NAWS,NEW_ENVIRON,TTYPE>

tel:sh> reader
<TelnetReaderUnicode encoding='utf8' limit=65536 buflen=0 eof=False>

tel:sh> toggle all
wont echo.
wont suppress go-ahead.
wont outbinary.
dont inbinary.
xon-any enabled.
lineflow disabled.

tel:sh> reader
<TelnetReaderUnicode encoding='US-ASCII' limit=65536 buflen=1 eof=False>

tel:sh> writer
<TelnetWriter server mode:local -lineflow +xon_any +slc_sim client-will:NAWS,NEW_ENVIRON,TTYPE>

Both command-line scripts accept argument --shell=my_module.fn_shell describing a python module path to a coroutine of signature shell(reader, writer), just as the above examples.

Features

The following RFC specifications are implemented:

• rfc-727, “Telnet Logout Option,” Apr 1977.

• rfc-779, “Telnet Send-Location Option”, Apr 1981.

• rfc-854, “Telnet Protocol Specification”, May 1983.

• rfc-855, “Telnet Option Specifications”, May 1983.

• rfc-856, “Telnet Binary Transmission”, May 1983.

• rfc-857, “Telnet Echo Option”, May 1983.

• rfc-858, “Telnet Suppress Go Ahead Option”, May 1983.

• rfc-859, “Telnet Status Option”, May 1983.

• rfc-860, “Telnet Timing mark Option”, May 1983.

• rfc-885, “Telnet End of Record Option”, Dec 1983.

• rfc-1073, “Telnet Window Size Option”, Oct 1988.

• rfc-1079, “Telnet Terminal Speed Option”, Dec 1988.

• rfc-1091, “Telnet Terminal-Type Option”, Feb 1989.

• rfc-1096, “Telnet X Display Location Option”, Mar 1989.

• rfc-1123, “Requirements for Internet Hosts”, Oct 1989.

• rfc-1184, “Telnet Linemode Option (extended options)”, Oct 1990.

• rfc-1372, “Telnet Remote Flow Control Option”, Oct 1992.

• rfc-1408, “Telnet Environment Option”, Jan 1993.

• rfc-1571, “Telnet Environment Option Interoperability Issues”, Jan 1994.

• rfc-1572, “Telnet Environment Option”, Jan 1994.

• rfc-2066, “Telnet Charset Option”, Jan 1997.

Further Reading

Further documentation available at https://asynctelnet.readthedocs.org/