Research On P2P System Based On Improved Chord Protocal

P2P (Peer-to-Peer) network is a distributed network. Peers in the network can bevisited by other coordinative peers and provede service to other peers without anymid-peers. So a peer in the P2P network is not only a client but also a server. P2Pincludes so many algorithm but the chord algorithm is the most importantalgorithm.Chord algorithm provides a typical implementation mechanism in P2Pdistributed system, with advantages of load balance, distribution, scalability andavailability. However, when it comes to the situations of abnormal node leaving, itdoes not provide a better solution for data backup and network maintenance, whichlimits the Chord algorithm for large-scale application. Therefore, to solve the problem,we researched on Chord and the main contribution includes:Firstly, to overcome the shotcomings of Chord algorithm on node failure, wepropose a new algorithm. In this algorithm, we design a new data structure（On thebase of the orginal alogrim,the mechanism of Timer and data-copy are introduced intothe alogrim.）, the abnormal node leaving mechanism is implemented with lessresource overhead. Data redundancy backup mechanism handles the details. Bybacking up data to its successor to ensure the data integrity of the ring when the nodeleaves abnormally. Experiment result shows that the new algorithm can efficientlyhandle the node failure without breaking the Chord ring and the resources of the ring.Secondly, In order to test and verify the efficiency of the improved Chordalgorithm, we design a distributive resources sharing system based on the proposedalgorithm. The system can efficiently handles the node failure and protect theresources on the ring. In the system, In order to solve the network latency and otherproblems which lead to inconsistent message sequence, the UDP protocolcommunication mechanism with random port is used. Each node is designed as amulti-threaded concurrent server to respond and handle the message, which helps toimprove the response speed of the node and overall system performance. It is achievesmechanism similar to Huntmine with shared directories, to achieve easy use for users.Finally, The system is implemnted with Java language. Chord algorithmmechanism is shelled to run internally in the background. The whole developmentprocess follows a iterative development model, while experiments and testing adoptthe black-box test. After testing, the system can provide file search and downloading services to system users, and achieves designed objective.