Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  TELNET Buffering Woes
Message-ID: <40023@think.UUCP>
Date: 3 May 89 18:40:30 GMT
References: <8905021526.AA03195@oliver.cray.com>
Sender: news@think.UUCP
Reply-To: barmar@kulla.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge, MA
Lines: 27

In article <8905021526.AA03195@oliver.cray.com> dab@opus.cray.com (Dave Borman) writes:
>The problem here is not with the remote machine, but with the local
>telnet implementation.  The way that things should work is:
>	User types ^C
>	Local telnet translates that to, and sends, IAC IP,
>		and then sends IAC DO TIMING-MARK and begins to
>		flush all output.

How is the local telnet supposed to know that ^C is the appropriate
interrupt character for the remote machine?  Many systems permit the
interrupt character to be set by the user or a program.  I don't think
the TELNET protocol specifies a way to transmit this change to the
client.

Also, the above assumes there's only one kind of interrupt.  On Unix,
there's ^C (interrupt), ^Z (suspend), and ^\ (quit).  They all need
output flushed, but they can't all send IAC IP.

What's really needed is a way to send out-of-band data to the telnet
client, telling it to ignore output until it reads a mark.  Is it
possible to use the URGent flag to implement this?

Barry Margolin
Thinking Machines Corp.

barmar@think.com
{uunet,harvard}!think!barmar