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/