topic Re: Broadcast or $BRDCST in Operating System - OpenVMS

Broadcast or $BRDCST

sathya prabu — Fri, 19 Mar 2010 08:53:53 GMT

Can i log all the broadcast(basiclly REPLY) messages into a file.

Re: Broadcast or $BRDCST

sathya prabu — Fri, 19 Mar 2010 11:06:03 GMT

Disabling the reply message to display on the terminal using SET BROADCAST=NOGENERAL, when switched on back SET BROADCAST=ALL also is not displaying any messages arrived during the session. Does anybody have any idea on how to have a track on the REPLY messages?

Re: Broadcast or $BRDCST

Joseph Huber_1 — Fri, 19 Mar 2010 11:25:04 GMT

Your question is somewhat ambigous:

Broadcast to Your process/terminal can be catched by a program establishing an attention-mailbox-AST on the terminal (sys$input) of the process.
An example of how to do it is in
http://www.mpp.mpg.de/~huber/vmssig/src/MAR/GRAB_BROADCAST_MESSAGES.MAR

You can take this program, and enhance it to log the trapped messages to a file.

Or take another example written in C, which traps broadcasts and displays them in graphic display window:

http://www.mpp.mpg.de/~huber/vmssig/src/C/BTRAP.C

On the other hand "REPLY" messages ? OPCOM messages are logged in the OPERATOR log file if enabled by REPLY/LOG.

Re: Broadcast or $BRDCST

John Gillings — Sun, 21 Mar 2010 19:58:58 GMT

sathya,

In theory you could put a software hook in the system service dispatch vector for the $BRDCST service and log everything that went past for all users and all destinations. A non-trivial, privileged, and fairly dangerous exercise. If you need to ask this question, then it's probably not something you should attempt straight away.

Remember that $BRDCST (REPLY) messages can be sent FROM anywhere, and TO a variety of destinations. Think about which messages you're interested in, and if you want to catch them on the sending side or the receiving side. There are numerous tricky cases. For example, what if someone sends a REPLY/USER=someone but the user isn't logged in? The message never gets delivered anywhere. What if someone sends a message to a specific terminal with no one logged in? The message is delivered, but there's no attached process to catch it with something like Joseph's example program.

If you have control over the sending of the messages you're interested in, I'd be taking the easy solution of logging at the source. Abstract the operation, changing it in your sending application from "$BRDCST" to "SendMessage". Implement SendMessage as:

LogMessage(msg)
$BRDCST(msg)

(where LogMessage writes the message to your log file).

Re: Broadcast or $BRDCST

sathya prabu — Wed, 07 Apr 2010 07:38:35 GMT

Thanks a lot John and Joseph! that definitely helped me.