OVERVIEW

This directory contains source code for a prototype CORBA-based
distributed notification mechanism.  This mechanism implements a
"publish/subscribe" communication protocol.  It allows Suppliers to
pass messages containing object references to a dynamically managed
group of Consumers.  This is similar to the OMG COSS Event Service,
though not as sophisticated.

This example also illustrates how to integrate Orbix with the ACE
libraries.

DIRECTORY STRUCTURE

There are 4 directories:

Supplier 

	-- The supplier test driver, which must be started
	   first.  It has an instance of an IDL Notifier
	   object.  This object accepts subscriptions from Consumers 
	   and forwards events sent to it either via Consumers or 
	   via its standard input.

	   The Supplier must be registered with the ORB using the
	   following command:
	   
	   % putit Event_Comm_Notifier <pathname>/supplier
	   
Consumer

	-- The consumer test driver, which must be started
	   after the Supplier.  It has an instance of an
	   IDL Notification_Receiver object.  This object is 
	   used to receive notifications from the Notifier object
	   residing in the Supplier.  When the Consumer starts up it
	   gets an object reference to the Supplier's Notifier.
	   It then subscribes its Notification_Receiver object with
	   the Supplier's Notifier by passing an object reference.

	   In addition to passing an object reference to a
	   Notification_Receiver, the Consumer also may specify a
	   filtering criteria, which is a regular expression.  If
	   the filtering criteria is the string "" then the Notifier 
	   will send all Notifications to the Consumer (i.e., "" is
	   treated as a "wildcard").  Otherwise, the filtering 
	   criteria is considered to be a regular expression,
	   and only those Notification tags that match the regular
	   expression will be forwarded to the Consumer.  The regular
	   expressions are those used by ed(1) (see the regexp(5)
	   manual page for more info).

	   The Consumer must be registered with the ORB
	   using the following command:
	   
	   % putit Event_Comm_Notification_Receiver <pathname>/consumer
	   
include

	-- This contains links to the appropriate header 
	   files.

libsrc

	-- This contains the IDL files and IDL implementation
	   classes that support the distributed notification scheme.
	   These are shared by the Consumer and Supplier.

RUNNING THE TESTS

To run the tests do the following:

1. Compile everything.

2. Start up the Orbix daemon (orbixd) if it's not already
   running.

3. Register the Consumer (i.e., Notification_Receiver) and Supplier
   (i.e., Notifier) with the Orbix daemon (orbixd), as described
   above.

4. Start the Supplier/supplier executable.

5. Start up as many copies of the Consumer/consumer as you'd like.
   Typically, I run each one in its own window.  If you'd like to use
   different machines make sure that you start up the Orbix daemon on
   each one and register the Consumer.

6. Once the Consumers have subscribed you can send them info by typing
   commands in the Supplier window.  These will be sent to all the
   Consumers who have subscribed.  Likewise, you can send messages
   from a Consumer to all other Consumers by typing messages in a
   Consumer window.

   Note that if you type "quit", ^D, or ^C in a Consumer window the 
   Consumer will unsubscribe and shutdown its handlers and exit.  
   Likewise, if you type "quit", ^D, or ^C in the Supplier window 
   the Supplier will disconnect all of its Consumers and exit.
   When a Consumer is disconnected from its Supplier it automatically
   shuts itself down.

7. When you want to terminate a Consumer or a Supplier, just type ^C
   and the process will shut down gracefully.

Please let me know if there are any questions.

	Doug

schmidt@cs.wustl.edu