Research Of P2P Key Technology And Implementation Of File-Sharing System Based On Kademlia

P2P is a peer-to-peer model which is different from C/S model, it has wide range of applications in file-sharing, multicast applications, immediate communication, distributed computing and other fields. P2P has changed the way we live, and it will continue to change our life. At present, with the issuance of domestic 3G licenses, it is believed that P2P technology will set off a frenzy at the field of mobile phone once again. Therefore the study and skilled use of P2P-related technologies are very important.This paper mainly studies P2P key technologies of network topology and resource search algorithm. First, four types of topology (Centralized Topology, Decentralized Unstructured Topology, Decentralized Structured Topology and Partially Decentralized Topology) and their respective advantages and disadvantages are analyzed. After analysis of the four kinds of topology, then, two typical search algorithms are studied: DHT search algorithm based on Structured Topology and Flooding algorithm based on Unstructured Topology.AS search algorithm based on Unstructured Topology is designed after the research of the P2P network topology and the existing search algorithm, which also refers to the ant colony algorithm and the small-world theory. Three kinds of mechanism are used in the AS search algorithm including the routing cache, distributing center node and short-chain. With the algorithm, the problems such as too much redundant message and too long response time caused by the Flooding algorithm are solved effectively.To test the AS search algorithm can solve complicated search in Decentralized Structured Topology. First, this thesis designs and implements sKad file-sharing system based on Kademlia protocol. Then implements complicated search in sKad by AS search algorithm. Last, sKad file-sharing system is tested. The sKad is made up of six major modules including interface management, routing table management, file management, structured network search management, download management and complicated search management. Implementing the network topology with no center server, sKad has advantages such as accurate search of resource, convenient operation, complicated search and so on. In sKad system, by the mechanism of checking reply message, malicious attacks are prevented on the Kad network to some extent, and by the mechanism of buffering data, the data storage rate was improved.