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Peer network technology (P2P) as an emerging technology, rapid development in recent years. Each node in the P2P is a provider of resources, but also access to those resources. Compared with the traditional model, with unparalleled decentralization, scalability, robustness, high performance / price ratio, high security. Meanwhile P2P technology has broad application prospects, has been applied to instant messaging, file sharing, peer to peer computing, precision search, enterprise applications, e-commerce and electronic games and other fields. However, many P2P systems are fragmented, forming one of P2P island. Such distributed and P2P design departure from the original intention. In the summer of 2000, Sun has proposed a \Platform-JXTA platform. JXTA is not just a peer to peer network computing platform, the key is that it implements a network, the programming language and platform-independent support for multiple P2P applications platform. JXTA platform interoperability, platform independence, universality and other characteristics. Based on JXTA platform, these features make it ideal for a P2P application development platform. Paper first analyzes the characteristics of P2P technology, summed up the three modes of P2P and various fields of application and analysis of the existing P2P applications defects and deficiencies, proposed the introduction of the P2P JXTA platform application development vision; and research the JXTA platform design objectives, basic elements and six agreements; propose a framework based on JXTA P2P application model, summed up the characteristics of P2P applications should have proposed this model four-tier structure (including network connectivity layer, JXTA core layer, the data model and the control logic layer and P2P application layer), analyzed several important agreements of the specific implementation process; then introduced an implementation of the model-PPChat instant messaging system design, given the framework of this system map and describes the system to achieve some functionality; final functional modules of the system according to the specific implementation are described in detail, the main modules including service applications, user identity authentication, the peer group, creating publications and join notices create the publication and discovery , the establishment of input and output channels, the message encoding format, send and receive messages, message encryption and decryption, friends search, object serialization, log generation and system interface design. Through this research, we propose a framework based on JXTA P2P application model, and use this model successfully developed an instant messaging system to verify the model. Further development of the system using this model has a non-centralized, robustness, high performance / price ratio, high security. The study not only analyzes the issues of P2P technologies and applications, and in the use of JXTA P2P application development platform has made some exploration.
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