Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!mit-eddie!uw-beaver!milton!Tomobiki-Cho!mrc
From: mrc@Tomobiki-Cho.CAC.Washington.EDU (Mark Crispin)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Telnet's ECHO option
Message-ID: <11717@milton.u.washington.edu>
Date: 27 Nov 90 00:46:21 GMT
References: <gm.3504@ionic.UUCP> <1191@disuns2.epfl.ch>
Sender: news@milton.u.washington.edu
Organization: Mendou Zaibatsu, Tomobiki-Cho, Butsumetsu-Shi
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In article <1191@disuns2.epfl.ch> conti@ltisun7.epfl.ch (Giovanni Conti) writes:
>I think there is a need to explain the WILL/WONT mechansim.

Yes, someone should explain it to you, since not only don't you
understand it, but worse, you don't know that you don't understand it
and you are spreading misinformation.  Please don't do so in the
future.  There are enough people around here who have written Telnet
software -- I've written several servers and clients for different
operating systems, going back to 1976 -- who can answer Telnet protocol
questions correctly.

The Telnet ECHO option, in a server/client environment, refers to
echoing done by the server of data from the client back to the client.

In other words, it is only meaningful for a client to send:
	IAC DO ECHO	(requesting/confirming that the server echo)
	IAC DONT ECHO	(demanding/confirming that the server not echo)
and for a server to send:
	IAC WILL ECHO	(requesting/confirming that it will echo)
	IAC WONT ECHO	(refusing/confirming that it will not echo)

In a bilateral Telnet (e.g. station-to-station) where there is no clear
server or client than it may be reasonable for echoing in both
directions.

>The ECHO is LOCAL. So if you ask your partner to do echo,
>he will duplicate his output stream (from him to you) onto
>his input stream.

Totally wrong.  The Telnet ECHO option controls remote echoing; local
echoing is only implicit.  An echo is never "a duplication by an agent
of his output stream onto his input stream."  An echo is a "duplication
by an agent of his input stream onto his output stream."

>If you ask the host to do ECHO, and assuming he answers WILL ECHO,
>that means that when he sends you the string "Username:", telnet echoes
>him a copy as if you've typed "Username:", leading to wrong behaviours.

No, no, no, 1000 times no.  That is what "IAC WILL ECHO" from the
Telnet client means.

I didn't see the original question, but it seems that you have sent
some poor guy on a wild goose chase.

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