As long as the publisher, the event class, and the subscribers are all installed on the same machine, you can have pretty much any topology of interaction (see Figure 9-12). On the same machine, publishers can publish to any event class, event classes can deliver events to any subscriber, and subscribers can subscribe to as many event classes as they like.
Figure 9-12. You can have any publisher and subscriber topology on the same machine
Unfortunately, the COM+ event service has a serious limitation—the event class and all its subscribers have to be on the same machine. This means that a deployment, such as the one shown in Figure 9-13, is not possible.
Figure 9-13. The event class and the subscriber must reside on the same machine
The rest of this section presents you with a few workaround solutions for this problem that allow you to distribute your events across the network. All the solutions adhere to the limitation that the event class and the subscribers have to reside on the same machine, and they solve the problem by designing around it. Like most things in life, each solution has pros and cons. It will be ultimately up to you, the system designer, to select the most appropriate solution for your domain problem at hand.