Jini even includes a network protocol that clients can use to find services in the absence of a lookup service. How Jini works Jini defines a runtime infrastructure that resides on the network and provides mechanisms that enable you to add, remove, locate, and access services. Lookup services are the central organizing mechanism for Jini-based systems. When new services become available on the network, they register themselves with a lookup service. When clients wish to locate a service to assist with some task, they consult a lookup service.
Discovery enables clients and services to locate lookup services.
Join enables a service to register itself in a lookup service. Lookup enables a client to query a lookup service for services that can help the client accomplish its goals. Imagine you have a Jini-enabled disk drive that offers a persistent storage service. As soon as you connect the drive to the network, it broadcasts a presence announcement by dropping a multicast packet onto a well-known port. Included in the presence announcement is an IP address and port number where the disk drive can be contacted by a lookup service.