From: utzoo!decvax!cca!hplabs!menlo70!sytek!gi!mike@sri-unix
Newsgroups: net.unix-wizards
Title: Re: uucp vs getty
Article-I.D.: gi.140
Posted: Tue Jun  1 16:20:48 1982
Received: Thu Jun  3 01:02:41 1982

I have been experimenting with a method of turning a dialin line around for
dialout. We are currently limited to 4 dialin lines on our vax. With the
recent upgrade for Vadic modems (to become dialers) , two of those lines are
capable of dialing out. I have chosen the following for my strategy:

	All incoming calls start at one end with dialing out
	starting at the other end.

	I use the execute bit of the tty special file to indicate if getty
	is hanging on the line or not. Init sets the tty file mode to 623.
	Login changes the mode to 622. By looking at the execute bit, I can
	determine whether or not I can disable the getty on the line and
	dial out.

I am currently implementing this code in uucp. I utilize a program called
enable(8) for enabling or disabling getty on a line. Enable was submitted to
Usenix (at Santa Monica) for distribution. I have successfully implemented
this code in our equivalent of cu(1). I am also planning to implement this
protocol for tip(1). The key to my protocol is simply using the execute bit
as my semaphore. It has no other use for a tty special file. Once completed
I will probably distribute the changes via usenix.

This protocol has proven reliable in allowing uucp and our cu program to share
a leased line between 2 remote systems. My current task is more concerned with
talking to the Vadic intelligently rather than turning around the line. As many
comments have indicated - the Vadic was designed for interactive use by a human
with no nice and simple protocal for talking with a computer.

	Michael Wendel
	General Instrument Corp.
	Corporate Research and Development

	ucbvax!menlo70!sytek!gi