A client program creates one or more Broker clients in order to publish or retrieve events. For example, a network monitoring application might create a Broker client to publish events that represent network transmission errors. A network management application might create a Broker client to subscribe to these network error events. If the number of network error events retrieved reaches a critical threshold, the management application might create a different Broker client and use it to publish statistics about the network failure.

Event-based client applications are de-coupled from one another because they generate and receive events through an entity called a Broker Server. When your client program creates a Broker client, it is actually establishing a connection between your application and a Broker running on the local host or some host on the network.