SUMMARY: Modem Dialin Problem

From: Steve Lodin (
Date: Fri Jan 15 1993 - 17:14:03 CST

I wrote:

> Sun-managers:
> I'm really stumped and I need the help from you experts!
> I have a Telebit TB+ on serial port B of a Sun 4/490 CPU running 4.1.2. It
> was working fine up until a month or so ago. Dialout works fine, but dialin
> starts getty wars whenever I enable getty on the device. I can't determine
> anything that would have changed so I began by replacing hardware then worked
> my way to software.
> 1) Reset modem to defaults. Reset modem to known working values.
> 2) Replaced the modem with a working Telebit 2500.
> 3) Replaced the CPU.
> 4) Replaced the cable.
> 5) Used a breakout box to look at the modem lines. CD is low.
> 6) Checked ttytab, verified status = on and remote.
> Following previous article on the topic didn't solve anything.
> 7) Re-made the dialout device /dev/ttyd1.
> The status of the CD line is what determines whether getty is blocking or
> running, correct? If CD is low, getty should block. When CD goes high
> (asserted), then getty should present the login prompt. (I do have the
> logic correct don't I, getty high is asserted.)
> At this point, I'll take any and all hints or suggestions. I need to get
> incoming UUCP back up and running again.

I got help from:

From: Joe Konczal <>
From: etnibsd! (Steve Harris)
From: Kevin Cosgrove 642-2676 <qiclab!solomon!>
From: (David Myers)
From: (J. Matt Landrum)
From: Jim Prescott <>

It looks like the ttysoftcar isn't working when executed from /etc/rc. I
have the following line in my /etc/ttytab:

ttyd1 "/usr/etc/getty std.19200" dialup on remote unsecure

I wasn't able to get the status of ttysoftcar of the line, but when I
manually turned software carrier detection of using "ttysoftcar -n ttyd1" it
seemed to work. I know I looked at the man page and /etc/ttytab about 20
times thinking "This looks correct" and not trying it manually.

According to the man page for ttysoftcar:

     For each tty specified ttysoftcar changes the carrier detect
     flag using the TIOCSSOFTCAR ioctl() request (see tty(4)).
     If the -a option is specified, ttysoftcar sets all tty's in
     the /etc/ttytab file to the carrier detection mode specified
     by their status field. If this field is set to local,
     software carrier detection is turned on. If this field is
     set to anything other than local, as is usually the case for
     modems, software carrier detection is turned off.
     ttysoftcar ignores devices in the /etc/ttytab file which do
     not exist.

So, now I have to figure out why it isn't working like it should. Thanks to
the guys above for the help!


Steve Lodin	(317)451-0479	Internet:
SysAdmin, Software Technology
Delco Electronics Corporation	UUCP:		deaes!swlodin

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