Path: utzoo!utgpu!water!watmath!clyde!rutgers!mcnc!decvax!decwrl!sun!pitstop!sundc!seismo!uunet!van-bc!sl
From: sl@van-bc.UUCP (Stuart Lynne)
Newsgroups: comp.dcom.modems
Subject: Re: GETTYDEFS, etc. (babbling getty)
Message-ID: <1660@van-bc.UUCP>
Date: 30 Jan 88 02:34:06 GMT
References: <142@mccc.UUCP> <564@virginia.acc.virginia.edu> <10321@mimsy.UUCP> <178@jim.odr.oz>
Reply-To: sl@van-bc.UUCP (Stuart Lynne)
Organization: Public Access Network, Vancouver, BC.
Lines: 35

In article <178@jim.odr.oz> brw@jim.odr.oz (Brian Wallis) 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.

>The kernel support needs to be able to reset the modem to a useable state as
>well, since the dialout program may have put it into an unuseable state. Say
>set the modem to not answer any incoming calls, or to answer them all at 300
>baud!

The best way to do this is to configure your modem to re-init itself when
DTR is dropped. If you have a Telebit as opposed to Hayes 2400 you can even
have it not answer the phone while DTR is low :-).

I just implemented a serial driver for System V / 386 with this type of
support. The added code for the driver is fairly trivial and allows for much
simpler configuration of everything above it.  Getty just waits for a
successful open and runs. Things like cu/uucico either get the line and use
it, or are told it's unavailble (ENXIO).

The only remaining problem is the short window where your outgoing calls can
be talking to someone who just dialed in. With HDB this seems to be less of
a problem than with older uucp's, it just times out and retries. There
doesn't seem to be any inherent security problems with this, just a slight
problem with getting out reliably.

If possible arrange your Devices file so that you choose your outgoing
modems in reverse order of the incoming dial sequence to minimize
collisions.


Perhaps this type of support should be standardized in one of the
appropriate Unix standards?

-- 
{ihnp4!alberta!ubc-vision,uunet}!van-bc!Stuart.Lynne Vancouver,BC,604-937-7532