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TCPIP to a DECServer

 
Brian Lindauer
Occasional Contributor

TCPIP to a DECServer

Has anyone ever written a program to use TCPIP sockets to talk to a DECServer? I have my server setup to listen for incoming connections. When I write a command to the port all of my ports respond eventhough I only the command to one port. Any help would be greatly appreciated
4 REPLIES 4
Hoff
Honored Contributor

Re: TCPIP to a DECServer

No answers. Many questions.

Which particular DECserver?

Which TCP/IP stack?

Incoming connections? As in a login or a data feed or what?

"Commanding" a port? That's not terminology I'm familiar with.

What exactly are you doing here? (I suspect the program is rather larger than the four lines of descriptive text included here; there's unfortunately not much to go on here, and not enough to even really guess as to what's going on. Pretty clearly there's something wrong in how you're sending commands to the remote device.)

What device is on the far side of the DECserver port, and what does it do?

Most folks use reverse telnet (see the OpenVMS FAQ) and this maps a port to a host TN device, the TN device looks and works like a terminal. It appears you're providing for a very different application requirement here.

Stephen Hoffman
HoffmanLabs LLC
Brian Lindauer
Occasional Contributor

Re: TCPIP to a DECServer

Currently I have serveral modems with rs232 connections to back of an alpha. I want to move the modems to a terminal server and communicate through the server to the modems. We are using a DECServer 700-8 for the test. I have set up the DS700 to use TELNET LISTENER and assigned listeners ports to each port on the DS700. I wrote some c code to use the TCPIP socket routines (socket, connect, send, and recv) to connnect to the server and send commands to the modem. Whenever I send the modem command to one port on the server, the modem responds correctly but the other ports also respond with data. This cause my read to fire 8 times instead of once. I thought maybe I could use TCPIP instead of using LAT to talk to the modem and terminal server.
Any suggestions would be helpful.
Hoff
Honored Contributor

Re: TCPIP to a DECServer

Ok, a DECserver modem pool.

Here, I'd usually use reverse telnet and establish the mappings and the host telnet TN terminal devices linked to the DECserver ports with modems. Reverse telnet looks and works like an inbound telnet connection arriving at the host, but the telnet connection is originated at the host and is outbound. Hence the use of "reverse" here.

You can then SET HOST /DTE out one of the TN devices, and off you go chatting with the modem.

For programmatic access, you can open the TN device and treat it (more or less) like an existing terminal device.

I reworked a semi-related section of System Manager's Manual a while back, around the chapter on Understanding and Using Modems on OpenVMS. This updated section introduces the modem hardware, wiring and general concepts and approaches around using modems with OpenVMS.

For your case, the DECserver port would likely be bound using the reverse telnet mechanism, and you would then issue SET HOST /DTE or related commands against the telnet TN device on the host. Possibly including the Hayes AT dial sequence, as required. You could (mostly) ignore the use of the DECserver in this configuration.

Reverse telnet itself is (quickly) described in the OpenVMS FAQ section "How can I set up reverse telnet (like reverse LAT)?" and full details are available in the TCP/IP Services Management Manual, available at the OpenVMS documentation site in the TCP/IP Services shelf.

http://www.hoffmanlabs.com/vmsfaq
http://www.hp.com/go/openvms/doc

Here's a related write-up on the general topic of DECserver devices from Colin Butcher's xdelta web site:
http://www.downloads.xdelta.co.uk/decus%20uk%202002/decserver%20seminar%2026feb2002%20issue%207%2002nov2003.pdf

I'd point to other links at the HP OpenVMS site, but a number of spots at the web site are returning SSI errors, incomplete or missing or otherwise omitted (or now archived or retired?) data, or other oddities.

--

Now ITRC itself is being (unusually) flaky. Trying a re-post. Apologies if this gets duplicated; I did check to see if the previous posting attempts got through.


Brian Lindauer
Occasional Contributor

Re: TCPIP to a DECServer

I was able to find the answer through the suggestions given to me.