[vworld-tech] Telnet negotiation

Brian Hook hook_l at pyrogon.com
Sat Jan 24 20:20:42 PST 2004

Telnet protocol adherence seems to be a bit of a disaster right now, 
or I'm not reading the RFCs very well.

I'm trying to suppress local echo for password entry.  If I transmit:


This suppresses local echo with MS Telnet and Cygwin Telnet (I'm 
assuming the latter is effectively the same as Linux telnet?).  
Presumably this happens because I'm telling the client, "Hey, I'm 
going to echo...so stop".

But I don't echo, so passwords aren't visible (which is what I want).

Then to re-enable echo, I do:


On Cygwin telnet, I'm back in business...but in MS Telnet, it's still 
not echoing.  Both implementations report the same things, i.e. they 
respond with IAC,DO,ECHO and IAC,DONT,ECHO, which is expected, but 
obviously both act very differently.

But once I echo is disabled in MS Telnet, I can't figure out if 
there's any way to re-enable it.  That's a client I'd really like to 
be marginally compatible with.

The suppress-local-echo option (45?) seems very poorly supported, so 
I've given up on that as an alternative.

Anyone have any wisdom about telnet compatibility for MUD servers?


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