本设计课题―用JAVA语言设计即时通讯系统是为了更好的满足人们的网上聊天和彻底的实现两台计算机之间点对点的信息交流的需求提出来的，也是当今网络迅速发展的结果。本论文共分为七部分.第一部分简单的分析了本即时通讯系统开发的可行性，并重点对技术可行性（选择JAVA）做了详细分析；第二部分借助数据流图和数据字典对系统的功能和性能进行了详细的需求分析，建立了系统的逻辑结构；第三部分用结构图和层次输入输出处理图，建立了系统的总体结构；第四部分采用了过程设计语言对系统的各个功能模块进行了详细设计；第五部分用JAVA语言编码实现了本系统，并对系统的功能进行了简要的测试和调试；第六部分为系统测试部分，对系统的功能进行了全面测试；最后是此次设计的结论总结及部分参考文献。

关键字：Java2 JSDK 即时通讯 点对点　数据流图　数据字典　结构图　层次输入输出处理图　伪码

-the design issues - use Java language of instant communications system designed to better meet people's online chatting and the complete realization of the point-to-point between two computers exchange of information needs are raised. the current network is the result of rapid development. This paper is divided into seven parts. The first part of a simple analysis of the instant messaging system development feasibility, and the focus on the technical feasibility (choice of Java) have done a detailed analysis; The second part of using data flow diagram and data dictionary for the system's function and performance of a detailed needs analysis, established a system of logic structure; with the third part of the structure plan and the level of input and output processing of plans to es