🚀 go-pugleaf

I am interested in writing a little background program for the Macintosh to 
handle certain types of electronic mail applications.  Unfortunately I am
having a hard time finding out exactly how to put such a program together.

The program is to be installed as in INIT31 resource when the machine is 
booted...it will NOT be a desk accessory.  Its function will be to "listen
at the modem port for a message from a modem or hardwired CPU.  As an example
the program might listen for the "you have mail" message from a host CPU
tied to the modem port.  When it "heard" the message it would pop up a window
on the Mac screen to notify you that there is mail on the mainframe for you.
The basic idea of this is to allow you to login your Mac when you get to work
and then go about your business in Excel or some other program.  If you got
mail on the mainframe the background program would briefly interupt Excel to
let you know there was mail (so you could use a DA terminal emulator to go
read it).

The questions I need answered are this...

1. Is there a way to install this program so it won't mess up use of the
   second screen/sound buffer?

2. What form should the program take?  A driver of some kind or just a 
   memory resident routine tied into the Modem port's interrupt vector.

3. How can I use the Window manager from within the program (can I??)

4. Is there an easy way (without using the window manager) to cause all
   windows (including the background pattern) to go through an update event?
   <<I suspect writers of "sleep" and "screen saver" programs have already
   figured that one out>>

5. Is there an easy way to sense when a forground program opens or closes the
   serial port (so the background program can turn itself off when a terminal
   program wants the port, and back on when ther terminal program is done) 

Any hints/tips would be appreciated...source code examples would be appreciated
even more!!

Thanks in advance

Greg Corson
pur-ee!iuvax!kangaro!milo