Research And Realization On P2P Communication Based On NAT Traversal

This paper based on the background of home remote monitoring system, does research on the reliable and high efficient Peer-to-Peer Communication over WAN. In China, the communication endpoint located in home network is usually behind NAT, the endpoint from public network cannot directly access the inside one and have to establish P2P communication with the help of NAT traversal.This paper firstly introduces the different types of NAT behavior, and proposes a complete set of solutions for NAT traversal used in P2P applications:the client in the private network can initiate connection to the device which in the public and vice versa; if the two peers behind different EIM NATs, we use UDP Hole Punching to traverse NAT; if all of the above method won’t work effectively, we use a public server to relay messages to each other. All these technologies are widely used in nowadays, and we apply them to our home remote monitoring system.Further more, we introduce a reliable UDP based application level data transport protocol—UDT to transfer data reliably after punching UDP hole to traverse NAT successfully. We not only learn to use UDT but also improve it to enhance the ability to seize the bandwidth.When using a public server to assist the P2P communication to traverse NAT, how to implement high concurrency service app with response quickly and running stable is our purpose, how to develop agile service app with cost acceptable and easy to extend is our goal, the author according to the characteristics of multi-core processor, selected Half-Sync/Half-Async pattern as the research object, proposed the task allocating strategy based on correlation degree between tasks and the task scheduling algorithm based on resource utilization to improve Half-Sync/Half-Async pattern.