[HECnet] LAT question

[Johnny Billquist]

Not possible out of the box, as far as I know.

There are several pieces needed to understand to make this work.

You need a way to connect one serial port to another serial port. In this case, the "incoming" serial port should be connected to a physical serial port on the machine. Once again, not something supported out of the box, but this would just require a small program to be written. Not that difficult.

Important to know and understand is that you are not, in fact, providing any reverse LAT service. What you want is that an incoming LAT connection should not in fact start LOGINOUT, but instead allow you to communicate on a physical serial port on the VMS box.

So, on the VMS box, a program needs to be running, which are in control of the "serial" ports on which LAT will connect. And once a connection is noticed, it should just pass data back and forth between that port and the physical port you want to connect to.

One additional problem here is that you would really like to create two different LAT services on the VMS box for this to work, since I would assume you would still also be interested in logging in normally with LAT on the system.
As far as I know, this is not possible.

Reverse LAT, on the other hand, is a way on a VMS box (or any other system as well), to specify that a specific destination should be connected to when you open a specific port on the local machine. Thereby implicitly making an outgoing LAT connection from the VMS box.
This was/is typically used for such services as modems or serial port printers. Open TT47: on your system, and output to it. And the output will appear on a currently free printer, as an example.

That works the same on Unix systems as well.

The lat implementation for Linux is very buggy by the way. I've been using it extensively the last few weeks to make a reverse connection using llogin to a DECserver, and it occasionally hangs so bad I need to totally restart it to wake it up. So while it might have some useful features, it's unfortunately not in a good shape. I remember looking at it many years ago because of some other problems I had back then, and decided that it was not worth trying to figure out the code. I should write my own implementation instead, especially since the LAT specs are available. However, as usual, I have not had time to do so... :-(

	Johnny

Sampsa Laine wrote:
OK,
I see - so there's no way of doing this on VMS then? Good thing the Linux LAT seems to do the trick though.
Sampsa
On 9 Jun 2010, at 07:48, Johnny Billquist wrote:
Sampsa Laine wrote:
On 9 Jun 2010, at 01:27, Gregg Levine wrote:

Hello!
I see.

A good question. Now that I know that it is someone physical where you
are, I am fresh out of ideas.
This MUST be doable, it's such an obvious idea :)
Let's say back in the day I had a modem connected to one of my VMS boxes, would not sharing it over LAT be pretty obvious?

Yes. And they way you did it was by having a DECserver, on which the modem was connected.

      Johnny