With Jini, as new services are plugged on the network, they immediately become available. For example, when you plug a Jini printer on the network, it is immediately possible to use it from other Jini-enabled devices such as a PC, a PDA, or even a camera. Jini uses RMI as the underlying communication protocol. Lookup The lookup service allows client and server to find each other. Upon startup, a server registers its services with the lookup service.
Clients use the lookup service to locate the services they are interested in.
For example, when a Jini-enabled printer is plugged in to the network, it registers itself with the lookup service. A word processor would use lookup to find available printers. The answer is through the discovery protocol. Discovery is implemented through multicast and unicast requests, as well as multicast announcements. Multicast request Servers use the multicast request to locate the lookup service.