Connecting pppd to a serial port

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From - Sat Apr 10 06:57:07 1999
Xref: world comp.unix.sco.misc:93776
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From: evanh@sco.COM (Evan Hunt)
Newsgroups: comp.unix.sco.misc
Subject: Re: Manual dial-up PPP
Date: 9 Apr 1999 22:12:08 GMT
Organization: The Santa Cruz Operation, Inc.
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Don't blame me, I voted for K.Lentin@cs.monash.edu.au.
>Why leave my private passwords on my employer's machine?
>
>Why waste phone calls when a perfectly good serial link exists on which to
>run ppp.
>
>[...]
>We paid over $10,000 for this operating system and
>it's pppd is either so stupid or so insane that it can't do something as
>simple as start up and talk to a serial port? Either I'm wrong or the world
>is very stuffed.

I didn't say pppd couldn't do it, just that I didn't understand
why you wanted it to.  It's designed to bring the link up silently
when you request IP connectivity; I regard that as a good, useful
design.  Wanting to manually dial the phone and type your password
every time seems like a hassle, a feature few people would desire.
The fact that you're the first person to ask for this feature in the
three years I've been responsible for MSTPPP on SCO platforms, suggests
that I may have been correct in that evaluation. :)

I can think of two ways to do this.  Here's the simpler one:  Set
up your modem so it doesn't hang up when it gets an EOF.  I forget
how to do that, but there's an AT command sequence that allows it--
perhaps someone else could help out here?

Create a script called "startppp" on the remote side that runs pppd
for you with all the necessary options.  Configure MSTPPP on the local
side with no phone number, the specific name of the serial port you'll
be using, and a chat script that just calls "startppp"--something like
this:

    1.2.3.4 Any tty1A 115200 N/A "" "" "" startppp

When you want to start up a PPP link, you use kermit to connect to
your modem and dial the phone.  Without logging out or entering
"ATH", quit from kermit.  The modem should remain connected.  Run
pppd with either the "dedicated" or "auto up" option, on that same
serial port.  PPP should treat the modem as if it were a fixed serial
link--connect, run "startppp", negotiate with the remote PPP daemon,
and establish a link, without bothering to dial.

I've never tested this, but I can't think why it wouldn't work.

Here's the more complicated way:  Write a dialer program, based on
atdialer.c in /usr/lib/uucp, which dials the modem for you.  When it
connects, your program should pop up a terminal window so that you can
log in.  AFter you've done so, you can close the window, and then your
dialer program would pass control of the terminal back to the calling
process, just as atdialer already does.

Put your new dialer program into /usr/lib/uucp, and put its name
into the first field of /usr/lib/mstppp/Devices.  MSTPPP will then
call your program whenever it wants to dial the phone, so you'll get
an opportunity to type your password.  The Systems file should look
very much like the other one, except with "ACU" instead of "tty1A".

-- 
                  Evan Hunt   -   evanh at sco dot com

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