Network Services

Network Services

Distributed Application Paradigms

Network Services • Services can be located through a directoryservice. • Services can be discovered using a lookupservice and a discoveryprotocol (e.g., JRMP). • Services can join the community and register their availability with one or more lookup services.

Network Services • The network is seen as federations of services and clients. • Services include applications, databases, servers, devices, information systems, mobile appliances, storage, printers. • Clients are requesters (and consumers) of services

Network Services • Each federation of client and service(s): • is independentof other federations and may co-exist with other federations. • is transient: the union lasts only for as long asthe service(s) is/are needed. • There is nocentralized controlsystem: • There is no centralized administration of available services • There are nopoliciesthat restrict federation between a client and services.

Jini Network Technology • Jini provides an infrastructure and a programmingmodel based on federation of network services. • It uses RMI to transport objects • It allows a clientprogram to make use of serviceswithout being aware of the “wire protocol” used by the service. • It provides the concept ofleasing a service: a client requests the lease of a service, which expires after a time period.

Jini Network Technology • A service is an object that implements a service API. • A clientlooks up a service that supports an API. • A discoveredservice object is sent to the client. • The client and the service only have to agree on the API, and nothow requests and responses are transmitted (e.g., protocol)

Jini Network Technology • Jini is to network services what universalplug-and-play is to system devices: it allows interoperability of clients and services regardless of transport and “wire” protocols.

Figure from “Jini By Example”

Jini Network Technology (I) (II) From http://java.sun.com/developer/products/jini/arch2_0.html

Jini Network Technology (III) (IV)

Jini code samples: • HelloWorld – • “nugget” JiniExample1 illustrates network service lookup • “nugget” JiniExample3 illustrates network service discovery (Noel Enete’s Nuggets for Jini (code samples), http://www.enete.com/download/index.html#_nuggets_) • Calculator • See “jini by Example” paper from California Software Lab. California Software Lab | Jini by Example – Whitepaper, http://www.cswl.com/whiteppr/tutorials/jini.html

Applications • Shared network devices such as printers. • Service (software, video, music, etc.) on demand • Shareware

Sources of Information • Jini(tm) Network Technology, http://www.sun.com/jini/ • Core Jini, a book by Keith Edwards • Jan Newmarch's Guide to JINI Technologies, http://jan.netcomp.monash.edu.au/java/jini/tutorial/Jini.xml • Jini Planet, http://www.kedwards.com/jini/ • Directory of Jini™ Resources on the net: Tutorials_and_Examples, http://litefaden.com/sv/jd/Tutorials_and_Examples/

Sources of Information • Jini whitepaper, http://wwwwswest.sun.com/jini/whitepapers/jini-execoverview.pdf • California Software Lab | Jini by Example – Whitepaper, http://www.cswl.com/whiteppr/tutorials/jini.html • Noel Enete’s Nuggets for Jini (code samples), http://www.enete.com/download/index.html#_nuggets_ • Jini.org -- The Community Resource for Jini(tm) Technology, http://www.jini.org/

Network Services