Subject: Re: com driver hangs?
To: Ty Sarna <firstname.lastname@example.org>
From: Dave Burgess <email@example.com>
Date: 03/28/1998 11:53:30
> In article <firstname.lastname@example.org> you write:
> > > ... I'm using modemd to answer the phone.
> > I use only "pppd". Does "modemd" use any special system calls or io controls
> > which "pppd" doesn't?
> I don't think so. And as I said, pppd hangs too. Only when the line has
> gone down and it's trying to reconnect, though. I'm thinking it's the
> closing-and-opening that wedges the port. That's the only comonality
> between the two. That's also why I'm wondering if the -current com
> driver might avoid the problem, that section of code having been
> reworked some.
> Problem is it happens so rarely that it's hard to diagnose. I haven't
> been able to reproduce it on demand, either.
I have confused the COM port (el cheapo 33.6 modem) in the past. The
closing and sudden opening and then sudden closing and reopening seems
to be the primary cause. My experience (-current through 1.3, I need a
stable source tree for work now) was that I could jam up the COM port
from Kermit by doing things like bailing out of a dial sequence while
the modem was negotiating the protocol, or sending a ATDT sequence that
had a dial, hangup, dial again real quick sequence (it was a mistake).
Of course, the whole thing was very much "barometric pressure in Peru"
driven. I could hammer away for hours at a time, then jam it three
times in three minutes. I ascribed to a flakey hardware (or at least
crappy hardware) since nothing but a power cycle could recover it. "On
demand" was impossible, unless of course I was under a deadline, in
which case it would jam if I talked to it mean :-).... In all
seriousness, I haven't seen one of these jams in several months. My
com port performance has been excellent over the past four or five months.
As an aside:
I work for (with?) an ISP here in town. I get one or calls a week from
people getting dumped off the modem pool. Half are through inactivity,
the other half just "hang up". I have NEVER been kicked off line using
the PPP driver in NetBSD. I understand most of the problem these folks
are having is "local loop" problems, but it still speaks well of the COM
driver that it doesn't exhibit all the weirdnesses of the Microsloth COM
driver (which is an industry standard now...)
Dave Burgess Network Engineer - Nebraska On-Ramp, Inc.
*bsd FAQ Maintainer / SysAdmin for the NetBSD system in my spare bedroom
"Just because something is stupid doesn't mean there isn't someone that
doesn't want to do it...."