【作者】 吴鹏；

【导师】 李静梅；

【作者基本信息】 哈尔滨工程大学 ， 计算机应用技术， 2007， 硕士

【摘要】 P2P是由若干互相对等的网络结点组成的一种网络结构，其中每个网络节点称为对等点，对等点消除了服务器和客户端间的角色差别，通过它们之间的信息直接交换完成计算和信息的共享。JXTA平台是P2P系统的典型代表，它实现了P2P系统的基本功能。本文研究了JXTA平台的基础：对等点查询机制，指出在现有机制下应保持JXTA平台多层结构的特点，这样能保持网络的高性能。详细分析了P2P的各种网络元素按照各种网络协议进行通信的方式和过程，并与常见的P2P系统的类似过程进行了对比。提出通过在P2P的对等组中应用安全机制，在不影响效率的前提下保证了系统的安全性，实现了对等组创建、查找、加入、退出的完整过程。为构建一个基于JXTA平台的异构分布式系统，本文引入了另一种分布式系统的技术：Web Service，分析了其系统架构和协议组成，并辨析了它与P2P系统存在的异同点。通过以上分析，提出了利用中间件实现一个P2P系统和Web Service互相访问的异构分布式系统，而且要保证系统安全性和调用Web服务的准确性。中间件实现方案是在现有对等点基本功能基础之上加入访问Web Service的功能，此中间件命名为Web Service Proxy，即代理访问点。Web Service Proxy是对等点访问Web Service的中介或代理，向P2P网络中所有对等点提供接受并处理Web Service请求的服务，然后负责发现、调用Web Service和返回结果。在完成两个异构系统互相访问的基础上，为更准确地查询到有关的Web Service，中间件加入了UDDI功能，通过给出简单信息即可定位到某个服务。另外，多个相同的中间件可以组成一个对等组，当边缘对等点加入时便可利用对等组的服务，既扩大了查询范围也利用JXTA平台提供的完整的安全机制保证了系统的安全。更多还原

【Abstract】 P2P is a kind of network architecture composed of lots of network points which are equals with each other in the role, among of which the difference between the server and the client in the aspect of role is eliminated by the point which is known as peer and through the message between which complete the disputation and the information sharing directly. The JXTA platform is the representative implementation of P2P system, all the basic functions of P2P can be found in the platform. The base of JXTA platform, that is query mechanism, is researched carefully. It is pointed out that the character of multiple levels, in this way the high performance of network can be kept. The method and procedure of all kinds of elements of P2P communicate with each other according to the P2P protocols are analyzed in detail, and the same procedure is contrasted with the popular P2P systems. The design scheme, using safety mechanism in the peer group of JXTA, is put forward. The total procedure of creating, finding, joining and exiting peer group is implemented.In order to construct an isomerous distributed system based upon JXTA, another technology of distributed system, that is Web Service, is introduced. The architecture and protocols are analyzed, and the similarities and differences with the P2P system are distinguished.Through the above analyzing, an isomerous distributed system using middlewares to finish the visit to each other between P2P and Web Service system is brought forward, and the safety and veracity of visit the service must be ensured. The blue print of middleware is to adding the function of visit Web Service to the basic function of peer. The middleware is called Web Service Proxy, it performs as the agency of the peer when it wants to visit the outside service, and provides the service accepting and disposal of request to the Web Service, and then it is responsible for discovering, calling service and returning result.On the basic of two isomerous systems visiting each other, in order to find the related service position, the UDDI is added to the middleware. In this way service can be found although simple information is given. In addition, several middleware can group as a peer group, when a common peer joins in the group service which can be provide to enlarge the scale of query and to ensure the safety of system.更多还原