Instant Messaging System Realization

Instant Messaging is currently the most popular way to communicate on the Internet, by the way various Instant Messaging software have been continuously appearing; service provider offers more and more communication services nowadays. As the development of the Internet, Instant Messaging will perform a wider use and is growing up day after day.This thesis is just launched around this core of software development of server end of the instant messaging system..Based the function of exchange, which is the basic character of instant messaging system, online users management, safeguarding online users and exchange message are designed in main server. In order to lighten the load of the server, the transmission of the basic messages of the customer end, we have considered utilizing UDP to transmit trying P2P at first. If failed, then transfer messages from the main server again. In this way, the main server's treatment ability and corresponding tempo of the server have improved sharply. The Instant Messaging system uses TCP and UDP protocol as the transfer protocol, which makes more convenience between users to communicate and make friends. It uses XML to design information format, which riches the data for transfer and gains convenience for protocol extension. It uses SOAP protocol for data transportation, which makes breakthrough against the constraints by firewalls.Based demands for transmitting the file, we analyzed how transferring files between private network and public network, or all in private networks. We have chosen the best scheme of realizing from it. We have designed the communication route server. It is responsible for transmitting the file between different sub networks. If client end may transmit files for the same sub network directly, and does not need communication route server to bridge.To deal with the problems in NAT traversal,this paper documents and analyzes some NAT traversal techniques ,and introduces a simplest but most robust and...