>I'm not sure what you mean here. You're talking about filtering Telnet
>commands. That's not difficult. Do :
>
> - Scan for $FF
>
> - Do a C 'switch' statement on the following byte :
>
>    $FF)
>       Both bytes ($FF $FF) are to be replaced by a single $FF.
>
>    Codes from $F1 to $F9)
>       Take these two bytes ($FF and code) out and ignore them.
>
>    $FA)
>       Ignore this and all that follows until and including an $F0 byte.
>
>    $FB)
>       After this, another byte follows. Send all three back, but replace
>       the $FB by $FE
>
>    $FD)
>       After this, another byte follows. Send all three back, but replace
>       the $FD by $FC
>
>    $FC and $FE)
>       These should never arrive, unless you issued some telnet commend
>       before. To be safe, ignore them too. (Three bytes)
>
>    Everything else)
>       Ignore just the leading $FF (was invalid)
>
>This ensures that only the Telnet command parts are filtered out, and
>negotiation is always replied with a refusal.
