How to get asynchronous notifications from Emacs ?

[David Soulayrol]

Hello,

I'm looking for a way to obtain asynchronous notifications
of emacs actions, like: buffer was closed, displayed buffer has changed,
and so on.

I have discovered emacsclient and gnuserv which both allow me to send
synchronous orders to emacs, but I don't think they can solve my problem.

Do you know if such a tool exists ? If not, can you give me pointers or
preliminary help on how to write this in emacs lisp ? I think I'd have to
open a network connection, and then capture actions to send a message...

Thanks a lot.

David.