Both services and clients need to find lookup services. Discovering a lookup service may be done using unicast or multicast protocols. Unicast discovery is a synchronous mechanism. Multicast discovery is an asynchronous mechanism that requires use of a listener to respond when a new service locator is discovered .
When a service locator is discovered, it sends a ServiceRegistrar object to run in the client or service. This acts as a proxy for the locator. This object may be queried for information, such as the host the service locator is on.