Network Services 1022020 1 Distributed Application Paradigms 1022020

Network Services 10/2/2020 1

Distributed Application Paradigms 10/2/2020 2

Network Services can be located through a directory service. Services can be discovered using a lookup service and a discovery protocol (e. g. , JRMP). Services can join the community and register their availability with one or more lookup services. 10/2/2020 3

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 10/2/2020 4

Network Services Each federation of client and service(s): is independent of other federations and may coexist with other federations. is transient: the union lasts only for as long as the service(s) is/are needed. There is no centralized control system: There is no centralized administration of available services There are no policies that restrict federation between a client and services. 10/2/2020 5

Jini Network Technology Jini provides an infrastructure and a programming model based on federation of network services. It uses RMI to transport objects It allows a client program to make use of services without being aware of the “wire protocol” used by the service. It provides the concept of leasing a service: a client requests the lease of a service, which expires after a time period. 10/2/2020 6

Jini Network Technology A service is an object that implements a service API. A client looks up a service that supports an API. A discovered service object is sent to the client. The client and the service only have to agree on the API, and not how requests and responses are transmitted (e. g. , protocol) 10/2/2020 7

Jini Network Technology Jini is to network services what universal plug-and-play is to system devices: it allows interoperability of clients and services regardless of transport and “wire” protocols. 10/2/2020 8

Figure from “Jini By Example” 10/2/2020 9

Jini Network Technology (I) (II) From http: //java. sun. com/developer/products/jini/arch 2_0. html 10/2/2020 10

Jini Network Technology (III) (IV) 10/2/2020 11

Jini code samples: Hello. World – “nugget” Jini. Example 1 illustrates network service lookup “nugget” Jini. Example 3 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 | Jini by Example – Whitepaper, http: //www. cswl. com/whiteppr/tutorials/jini. html 10/2/2020 12

Applications Shared network devices such as printers. Service (software, video, music, etc. ) on demand Shareware 10/2/2020 13

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/ 10/2/2020 14

Sources of Information Jini whitepaper, http: //wwwwswest. sun. com/jini/whitepapers/jiniexecoverview. 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/ 10/2/2020 15