Re: Question about linemode implementation...

Greg Minshall <> Thu, 28 April 1994 15:54 UTC

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To: David Borman <>,
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From: Greg Minshall <>
Subject: Re: Question about linemode implementation...
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Dave and Steve,

>> If the application allows echo, then it seems perfectly fine if telnet
>> negotiates echo back and forth between local and remote.  It doesn't
>> seem fine to me if the client can re-arrange virtual terminal behavior
>> my application has specified.  It also doesn't seem right to me that
>> the application should see the "echo bit" off, just because echoing
>> is being done by the telnet client.

>Oh my.  By these statements it now becomes clear to me that you do
>not have a clear understanding of how linemode works, and what
>support is needed in the terminal driver on the server to allow
>linemode to work.


Actually, Dave wrote the thing and wrote the code and, etc., but i think i
actually agree with Steve's point of view.

If the application wants to be running in some mode "linemode" supports
(mostly, standard shell prompt mode), then linemode should be "operative". 
But, as soon as the application wants to do something funny (like, run vi,
say), then the application will put the pty in something like "raw" mode,
and *that* should cause the telnet server to say "drop out of linemode for
a bit" to the client (until the application says "go back into "normal"

That's my base view of how linemode should be operating.  It protects the
server side from traffic generated during "normal" TTY operations, but not
during "raw" TTY operations.

Then, Steve's point (to me) is that NO MATTER WHAT THE CLIENT says
(prompted by the user into saying it, or by some other trigger), linemode
should *NOT* be made operative by the server if the pty is in *RAW* mode
(set there by the application).

Dave, clearly you think i'm wrong.  But, *i* think i'm write :).  What say you?

>        2) The application on the master pty side has to be
>           notified whenever the state of the pty changes, so
>           that it can negotiate the appropriate new state with
>           the client.

Now, i'm not a pty expert, so i can't tell if "the application on the
master pty side" is a) telnetd, or b) vi/csh/whatever.  Maybe my confusion
is here (since i'm assuming you meant b, but *i* want a).