Conference noted::hackers_v1

You could use a mailbox for communication between two jobs.
I think that there is a version of FOOTBALL that uses 
mailboxes for a multi-terminal game.


Steve.

In my library, called SPRITE::USER1:[OSMAN.BLISSLIB], is a module that I
believe you could use quite easily.  It's called

	MAILBOX.OBJ

If you link it with your programs on each terminal, you could easily
establish communication.  For instance, when you want to send characters
from one process's terminal to the other, call

	SEND_MAIL_WAIT_NO_RSVP (pid, message-len, message-adr)

which sends the specified message (such as a string) to the specified process.

The other end merely executes

	READ_MAIL_WAIT (max-length, message-adr, actual-length, pid)

to read messages.  The actual-length and pid get filled in when the message
arrives, indicating exactly how long it is and who sent it.  If you then
type the received message on the terminal, you've effectively sent a message
from one terminal to another.

If you don't want to sit around waiting for a message, call

	SET_MAILBOX_READ_AST (astadr, astprm)

which will cause the routine specified by "astadr" to be called when
a message is available.  (The routine may then call READ_MAIL_WAIT_NO_RSVP
to read it.)

Feel free to try all this by copying MAILBOX.OBJ.  You'll need
to also link with TERMNL.OBJ and LINKED_BLOCKS.OBJ.  If you want the sources,
they're all in BLISSLIB: too.

Good luck!  Oh, by they way, if you win with it, let me know.  It helps
the ambition :-)

/Eric

Yeah,
I am using mailboxes.  There is a basic SERVER process and two PLAYER processes.
The PLAYER processes each have a mailbox to talk to the SERVER and there
is a central MAILBOX that acts as a request queue that all PLAYERS can talk
to.  My problem is that the mailbox logicals are being set up at a local
level.  If user JOE sets up the game, user SAM's process can't find the
logicals for them.  I tried inserting them in the system table, but my
call to $CRELNM came up with a SS$_ACCVIO error and I couldn't figure out
why.  The native language is PASCAL.  I am a novice when it comes to the
nitty gritty of VAX/VMS so all help would be appreciated.  The game is
a two-player EMPIRE.  

re: -.1
I'll look into them. thanks
Chad

Try putting the logicals in the group table.  They can't get into the system
table unless the users have sysprv (or something like that).  To get into the
group tables, they only need GROUP privs (or grpnam).  that is how the
FOOTBALL program works.

Scott.

I have the SYSNAM privilege but that (GROUP table) is a good idea.
Thanks
Chad

Another way to have interprocess communication that can be quite effective
(I have used it to communicate between terminals) is to used shared memory
(sections they are called I think). This allows two programs (or two copies
of the same program being run from different terminals) to have a shared
memory space that they can both access. Common event flags can be used for
synchronization if required.

Stephen Brown

	Although this may not be the best solution to your problem, there
is a way to treat a LAT terminal like a hardwired one before someone
logs in on it.

	Try the following:

	LAT> SET TERM OTHER
	LAT> CONN ZEKE  (hit only one return)

On another terminal (or session) find the LT device that just got
created.   It status will be different that the ones in use.  I think
the status is "available".  From that terminal, allocate the device.
Then you can read and write to the device just like it was a spare 
hardwired terminal.

	KC