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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.dcom.modems,comp.sys.att,comp.unix.questions
Subject: Re: GETTYDEFS, etc. (babbling getty)
Message-ID: <10321@mimsy.UUCP>
Date: 24 Jan 88 05:21:15 GMT
References: <142@mccc.UUCP> <564@virginia.acc.virginia.edu>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26

In article <564@virginia.acc.virginia.edu> scl@virginia.acc.virginia.edu
(Steve Losen) writes:
>If you want to use the modem for both dialout and dialin good luck.  It is
>possible, but it is not at all trivial to do.

It *is* trivial *if* your vendor has provided reasonable kernel
support.  Sun does, at least in SunOS 3.4.  I modified 4.1, 4.2,
and now 4.3 BSD to do it.  It is wonderful to be able simply to
point the dialout programs at /dev/dialXX and the getty at /dev/ttyXX
and have everything work.

The amusing (or sad, depending on your point of view) part is that
the kernel support required is trivial.

>It is sad to say, but the simplest solution to the dialin/out problem is
>to reserve some of your modems for dialout only and turn off getty's to
>those lines.

This, of course, works well in any case.  It is more expensive but
it is also more reliable.  There is an irremovable race condition
induced by using one modem for both dial in and dial out: if you
attempt to dial out at the same time that someone else dials in,
you can wind up talking to the wrong machine!
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris