Windows Communication Foundation (WCF) is the new service oriented programming model included in the .NET 3.0 framework. Windows Communication Foundation (WCF) is designed to offer a manageable approach to distributed computing, broad interoperability, and direct support for service orientation. To know more about WCF, please refer here
Currently am programming the Publisher/Subscriber model. Let me explain,
Subscriber is the service to which all clients subscribe and Publisher is the service which sends messages to all clients who have subscribed to Subscriber service. That is, suppose we have 10 clients and all 10 clients would subscribe to the Subscribe service to receive notifications (client programs are individual programs) and then whenever the required event occurs, the Publisher notifies all those clients registered.
This can be illustrated by the diagram below,
(Click on the picture to enlarge)