Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cwjcc!hal!nic.MR.NET!tank!nucsrl!accuvax.nwu.edu!jln
From: jln@accuvax.nwu.edu (John Norstad)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Init and DA...
Message-ID: <10050060@accuvax.nwu.edu>
Date: 19 Dec 88 19:15:25 GMT
References: <19709@ames.arc.nasa.gov>
Organization: Northwestern U, Evanston IL, USA
Lines: 43


Brad Soe asked about writing an INIT to notify users of new mail.

It wasn't clear whether the mail machine is sending you unsolicited packets 
notifying you of new mail, or whether you want to periodically poll the 
mail machine and ask if it has new mail.

If you want to poll, you should write an INIT that opens a socket for
the polling and installs a VBL task.  The VBL task wakes up periodically,
sends a message to the mail machine out the socket, and waits for a reply. 
If and when a reply arrives saying that there is in fact new mail, the VBL 
task calls the notification manager to alert the user.

If you don't want to poll, just wait for notification packets, then you
should write an INIT that opens a socket and installs a pair of completion 
routines in the system heap.  You need an ATPGetRequest completion routine 
and an ATPSendResponse completion routine.  The ATPGetRequest completion 
routine waits for notification packets to arrive.  When one arrives, it
calls the notification manager to alert the user and sends a response.
The ATPSendResponse completion routine waits for the response to be
acknowledged (I'm assuming you're using exactly once service), and issues
the next GetRequest.  The INIT issues the first GetRequest.

In both of these scenarios you must use asynchronous AppleTalk calls,
which requires at least some assembly language glue.

There's no need for a DA in either of these cases.  You can call the
notification manager from a VBL task or completion routine without having
to specify an application or DA.

It's all fairly complicated, but doable.  I have a half-finished 
AppleTalk program which uses the second scheme above.  The INIT is
in MPW C, while the completion routines are in MPW Assembler.  You're
welcome to a copy of my code.  The INIT and completion routines are
finished, debugged, and pretty well documented.  Write to me if you'd
like a copy.

John Norstad
Academic Computing and Network Services
Northwestern University

Bitnet:    jln@nuacc
Internet:  jln@acns.nwu.edu