Based On The Bittorrent Protocol File Sharing System In The P2p-

In this era,the development of Internet is amazing,while the emergence of P2P is a new revolutionary among this which have attracted peoples'attention to a very real extent. P2P(that is also called Peer-to-Peer Network or Peer-to-Peer Computing)is widely applied to our daily life and is achieving maturity day by day,which can achieve the purpose of sharing all sorts of resources and services through direct exchange between two computers mightily belonging to different Internet systems. Now the P2P application scope mainly concentrates in some aspects such as file sharing, resource searching, and memory space, etc. some online games, QQ, PPlive are all the specific application of P2P technology, which greatly facilitated and enriched our daily life.Comparing to the C / S model, P2P model abandoned the former Server / Client idea, in which each participation in download activities make a contribution to the entire network's downloading ability. With the P2P protocol, the file server's performance is no longer affected by the capacity and bandwidth of the network, as a result, the idle resources can be highly taken advantage of.Through this people solved the issue that in the past the sharing of resources between any two peer couldn't exchange directly but must pass through the server. With P2P technology, users can discover, access to or release any kinds of resources on the Internet voluntarily.On the basis of the analysis of the current situation and developmental trend of P2P technology, First, the paper introduced some key techniques of P2P including four types of network topology and the consequential two representative resource-searching algorithms: DHT algorithm and the flooding algorithm; Second, the paper studied the existing four protocols used in the file-sharing technology: Napster, Gnutella, eMule, and BitTorrent. BitTorrent, which is also called BT, is a file distribution protocol, and it can distinguish various contents by means of URL in order to achieve seamless integration with the network. The principal advantage of BT is that each user downloading the same file can provide seed for other users at the same time, through which the entire speed is greatly improved; Third, the paper also studied the composition, working principle and other related knowledge of the BT file-sharing system, BT is a type of download tool based on P2P technology, and it is so popular that almost every netizen knows it, the more people downloading, the more seeds, also the faster speed.Finally, combining with the relevant theories and techniques of P2P, the paper designed a file-sharing system based on the BitTorrent protocol, and made a comprehensive narrative and explanation of the composition and the structure of the system. At the same time, concerning the issues the Tracker server confronted itself in the traditional BT filing system, combining with the basic knowledge of DHT network, the paper proposed a program carrying on the DHT topological sorting to the Tracker server, which is to reduce the pressure and the load of the Tracker server, in addition, the system's efficiency and the stability is highly raised too. According to the experiment we discovered that the P2P file sharing system we designed is stable, reliable, and highly effective.