Design And Implementation Of The P2p Instant Message System Based On Nat Traversal

Instant Message System has been widely known and applied in enterprises. This System is designed based on a University network construction project. The application of Peer-to-Peer(P2P) in the Instant Message System improves many problems of Client/Server(C/S) frame, realize peer-to-peer communication to a great extent, and release the server to a certain extent and increase transfer rate. However, P2P system has a typical problem that can't setup connection normally when being blocked in the Network Address Translation (NAT) environment. Therefore, it is necessary to research it thoroughly.Except for the basic function of Instant Message System, The system is focused on solving the problem of NAT traversal. The main contents of this thesis are as follows:1,Investigate and analysis the needs of the system; research on the current function frame of the Instant Message System; overview the important technique(p2p technique and NAT techniques), and master the main principle;2,Analysis the result of the research, and comparison between various NAT traversal technique; provision of the solution to the problem of NAT traversal with the main UDP Hole Punching supporting and Relaying as a secondary assistance;3,Thorough analysis of the system, then design it, successfully realize each functional module of this system, as well as various NAT traversal procedures;4,Test on the module of NAT traversal and UDP reliable transmission system; adjustment on the tested systems and improvement of the overall effect of the system;At present, the system is on the stage of test. The system which aims to solve the problem caused by NAT and has improved some weakness of the University network. The system has worked well till now and has achieved the initial goals.