[comp.unix.ultrix] stopping unwanted output to tty

mcba@newt.phys.unsw.OZ.AU (Michael C. B. Ashley) (02/27/91)

Picture this:   you are logged into your trusty DECstation using a 1200
                baud modem. You accidently enter a command which results
                in a few megabytes of data being sent down the modem
                (e.g., perhaps your program had a few more compilation
                errors than you thought it would :-)).

Question:       How do you avoid having to wait half an hour or so before
                getting control of your DECstation back again?

Presumably there is some simple answer to this question. I have tried
every control character known to man, read dozens of manual pages on
terminal settings and line disciplines, and consulted local gurus,
without being any the wiser.

Any advice gratefully accepted.
Michael Ashley mcba@newt.phys.unsw.oz.au Astrophysics Department
University of New South Wales

grr@cbmvax.commodore.com (George Robbins) (02/28/91)

In article <1155@usage.csd.unsw.oz.au> mcba@newt.phys.unsw.OZ.AU (Michael C. B. Ashley) writes:
> Picture this:   you are logged into your trusty DECstation using a 1200
>                 baud modem. You accidently enter a command which results
>                 in a few megabytes of data being sent down the modem
>                 (e.g., perhaps your program had a few more compilation
>                 errors than you thought it would :-)).
> 
> Question:       How do you avoid having to wait half an hour or so before
>                 getting control of your DECstation back again?

Real questions:   what's your environment?

		  If you have a high speed modem on the decsystem that's
		  buffering output, you need to defeat the modem.  Some
		  modems can be set up to purge buffered output when they
		  receive a break.

		  If there's a telnet connection involved, you're probably
		  screwed, take a coffee break.

		  Otherwise, get somebody to spring for a faster modem!  8-)

> 
> Presumably there is some simple answer to this question. I have tried
> every control character known to man, read dozens of manual pages on
> terminal settings and line disciplines, and consulted local gurus,
> without being any the wiser.
> 
> Any advice gratefully accepted.
> Michael Ashley mcba@newt.phys.unsw.oz.au Astrophysics Department
> University of New South Wales


-- 
George Robbins - now working for,     uucp:   {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing:   domain: grr@cbmvax.commodore.com
Commodore, Engineering Department     phone:  215-431-9349 (only by moonlite)

mcba@newt.phys.unsw.OZ.AU (Michael C. B. Ashley) (03/07/91)

A short while ago I posted this question:
:
:Picture this: you are logged into your trusty DECstation using a 1200
:              baud modem. You accidently enter a command which results
:              in a few megabytes of data being sent down the modem
:              (e.g., perhaps your program had a few more compilation
:              errors than you thought it would :-)).
:
:Question:     How do you avoid having to wait half an hour or so before
:              getting control of your DECstation back again?
:

I have received some 80 e-mail messages in reply, and they fall into the
the following groups (my responses in parentheses):

(1) Have you tried CONTROL-O?  (Yes. It works eventually, but I would
    prefer something that worked immediately.)
(2) You haven't given enough information in your question. (Sorry, I
    should have said that I was using a modem connected through a
    terminal switch using telnet via ethernet.)
(3) If you are using telnet, then there is nothing you can do about
    it.
(4) Get a faster modem.
(5) If you get some sort of credible answer to this question, please
    e-mail a response. The CONTROL-O behaviour *really* annoys me.

By far the majority of respondents were in the last category. In an
attempt to quantify the problem, I logged into the DECstation from a
modem (--> terminal switch --> telnet --> DECstation 5000/Ultrix 4.0)
and monitored the ethernet traffic using tcpdump on another
DECstation. From the modem I tried

cat /usr/man/manl/perl.l       (this is 188015 bytes long)

followed immediately by CONTROL-O. The file perl.l started coming
down the ethernet 256 bytes at a time, the CONTROL-O was received AND
acknowledged by the DECstation after the first packet of perl.l, the
DECstation then sent a further 17 packets of 256 bytes (which took 1
minute of real time) before stopping. I tried a number of experiments
using CONTROL-O and CONTROL-C typed one or more times in various
combinations, and the figure of 17 packets appeared quite stable.

So, to rephrase my original question: does anyone know how to force
the DECstation not to send the additional 17 or so packets?