[ale] OT: Question about Telnet

Kevin Krumwiede krum at smyrnacable.net
Sun Feb 24 10:57:29 EST 2002


It's a proxying helper for Trade Wars. :)  I wrote a very simple "raw" proxy
that doesn't deal with the telnet protocol at all, and it works fine.  But
the "real thing" needs to parse text from the client for helper commands,
and text from the server for game data.  Dealing with telnet option
negotiation complicates those things too much for my short attention span,
so I'm going to use a bare-minimum NVT on both sides of the proxy and not
worry about it.  Seems to work OK... TWGS tries to negotiate few if any
options.  The only problem was with a couple clients I tried that send out
option requests and act weird if they don't get a response back.

Krum


> -----Original Message-----
> From: Chris Fowler [mailto:cfowler at outpostsentinel.com]
> Sent: Sunday, February 24, 2002 10:02 AM
> To: Kevin Krumwiede; ALE List
> Subject: RE: [ale] OT: Question about Telnet
>
>
> What deos the telnet proxy do.  If you just need a simple proxy with no
> interaction with the client then just forward data form your listening
> socket to you connecting socket.  To understand talnet *easier*
> then look at
> some older telnetd or telnet source code.
>
> Chris
>
> -----Original Message-----
> From: Kevin Krumwiede [mailto:krum at smyrnacable.net]
> Sent: Sunday, February 24, 2002 7:45 AM
> To: ALE List
> Subject: [ale] OT: Question about Telnet
>
>
> I'm writing an app that functions as a telnet proxy.  Eventually I want to
> make it semi-transparent, but that got to be a mess so I decided
> for now to
> just put a dumb NVT on both sides and use raw bytes for the filtering that
> goes on in the middle.
>
> RFC 854 says:
>
> b. If a party receives what appears to be a request to enter some
>       mode it is already in, the request should not be acknowledged.
>       This non-response is essential to prevent endless loops in the
>       negotiation.  It is required that a response be sent to requests
>       for a change of mode -- even if the mode is not changed.
>
> If I understand this correctly, my dumb NVT's responses should be as
> follows:
>
> DO: Reply with WONT
> WILL: Reply with DONT <--???
> WONT, DONT: Ignore
>
> If anyone can clarify this I'd be much obliged.
>
> Krum
>
>
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