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From: misko@ohlone.UUCP
Newsgroups: comp.sources.wanted
Subject: Re: UUCP Port Turnaround
Message-ID: <7200001@ohlone>
Date: Mon, 9-Feb-87 22:57:00 EST
Article-I.D.: ohlone.7200001
Posted: Mon Feb  9 22:57:00 1987
Date-Received: Wed, 11-Feb-87 05:53:48 EST
References: <166@piaget.UUCP>
Lines: 40
Nf-ID: #R:piaget.UUCP:166:ohlone:7200001:000:2063
Nf-From: ohlone.UUCP!misko    Feb  9 19:57:00 1987


/* Written 10:11 am  Feb  9, 1987 by piaget.UUCP!jc in ohlone:comp.sources.w */
/* ---------- "Re: UUCP Port Turnaround" ---------- */
In article <4090@nsc.nsc.com> jon@nsc.UUCP (Jon Ryshpan) writes:
>>Does anyone know a simple method to "turn a port around" so as to
>>make an outgoing call on a port which is usually used for incoming
>>connections?  I can imagine a messy shell script (run by root) to kill
>>the getty, make the call, and restore the getty.  Has anyone written
>>such a script?  Is there a better way?  How do you handle problems, if
>>any, with the modem?  (We are currently using Hayes Smartmodems.)
>>
>>Please reply by mail.  If anything interesting appears, I will
>>summarize, probably to Net.sources.
>>
>>Thanks:

>HDB uucp permits this.  A separate getty (uugetty) is fired up
>for such lines.  Uugetty locks the port with a lock file.  

uugetty does not lock the port (with a lock file) until someone attempts
to login.  The way uugetty determines if someone is trying to login
is that it waits to see a character.  Upon receiving 1 character,
uugetty assumes that someone is logging in, locks the port and
starts the login process (sending out login:, etc.).  This works
quite well except for when you are using certain modems.  The modems
we are using are Hayes compatible.  Unfortunately, they must always
have DCD raised for cu to work.  This is because cu waits for DCD.
If DCD is not up, cu times out with a DEVICE UNAVAILABLE error message.
Same with uucico.  The problem with always having DCD up is that our
modems send out "RING" when the phone rings.  uugetty sees this and thinks
that someone is trying to login.  If it was a wrong number, you run into
problems.  uugetty sends out "login:", the modem echo's it, uugetty echo's
it, the modem echo's it, etc. etc. etc. ad infinitum.  Really grinds the
machine to a halt.  We have a fix for this, but it required changing
cu, uucico, and uugetty.  We are running HDB uucp on an AT&T 3b2/400
running Sys V 3.0.

Bill Miskovetz
Cray Research
{ihnp4, lll-lcc}!ohlone!misko