*BSD News Article 86163


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Almost in PPP land but something is odd.
Date: 3 Jan 1997 21:18:07 GMT
Organization: Private BSD site, Dresden
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References: <32C707DF.5A75@eskimo.com> <5agh11$6fa@uriah.heep.sax.de>
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:33590

Enoch Wu <wue@eskimo.com> wrote:

> > > SIGHUP
> > > PPP terminated
> > >
> > > At that same instant, I noticed the modem dropped the DTR light.  It is
> > > as if PPP was telling the modem to drop DTR signal. Why ?
> > 
> > No, ``SIGHUP'' means the modem dropped carrier.

> But DTR is a control signal issued from the CPU.  DTR signal always
> flows from CPU to modem.

Sure, but the logged ``SIGHUP'' shows that it was the modem dropping
carrier.  In the course, PPP closed the line, and this in turn takes
DTR down.  But this was already a few hundred milliseconds after your
modem line broke.  (If PPP had closed the line first, and therefore
forced the hangup, it wouldn't have received a SIGHUP in turn, since
the tty was already closed.)

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)