Path: utzoo!utgpu!tmsoft!mcl!unibase!root
From: root@unibase.UUCP (Super User)
Newsgroups: comp.sources.d
Subject: Re: Remote control of PC via modem
Message-ID: <104@unibase.UUCP>
Date: 3 Dec 88 09:52:56 GMT
References: <4652@phoenix.Princeton.EDU>
Organization: EMIS Consulting, Regina, Saskatchewan, Canada
Lines: 52

From article <4652@phoenix.Princeton.EDU>, by mfryba@phoenix.Princeton.EDU (Martin Francis Ryba):
> 
> I want to remotely control a AT via the modem port.  I don't want the
> graphics (just tty), so I can do this from any machine.

etc.

No communication software of any kind is required for this kind of
control.  Assuming that you want to run standard software (ie: it calls
the standard MS-DOS calls for input and output), commands exist within
MS-DOS that will permit control to be passed to a communication port.

The basis of the solution is the 'ctty' command, which shifts the command
input/output from the keyboard/screen to a com port.

The problem is that the cable required between the modem and the computer
has to be jumpered all over the place.  I can't remember the cable I wound
up using;  solve the problem with a breakout box and a pile of jumpers.

Best approach is:  take a PC and a terminal (ignore the modem for now),
and get the PC to the point that these commands:

mode com1: 1200,n,8,1
ctty com1:

will give control to the terminal.  DON'T DESPAIR!!! It can be done with
the right jumpers on the cable.

If I remember correctly, simple jumpering on the PC end does not work,
because the ctty command does not cause the PC to assert anything at
all on its' com port.  Find a pin on the terminal that is asserted when
it's on, and connect it to 4,5,6,8, and 20 on the PC end (this is a
guaranteed jump - no matter what mode - DTE or DCE - the PC uses).
HINT: the PC transmits data on pin 2.  Most terminals transmit on pin
2 as well, so you will need to invert 2 & 3.  Connect pin 7 to 7.

Once you have that working, try this for a modem connection:

	set the modem for carrier detect on only when connected;
	set the modem to ignore DTR, and answer on the first ring;
	connect 4,5,6 8 and 20 on the PC to 8 on the modem;
	connect 2 to 2, 3 to 3, and 7 to 7;

And give it a try.

The nice thing about the ctty solution is that it works very well with
all software that follows the ms-dos convention for character input/
output.  NB: screen-based programs that address video ram directly will
NOT function with this solution - however, you can edit with edlin, copy,
start other comm programs, etc..  ALL ms-dos commands function.

Good luck.