摘要:现在局域网已经普遍融入人们的生活，学校，企业都建立了自己的局域网，人们在局域网中的交流也是必不可少的，这时就需要一款安全可靠的局域网聊天软件了，这也是做本设计的现实目的。
本设计是一个基于UDP的局域网聊天软件,主要使用现在比较普遍和流行的C#语言，采用面向对象的方法，综合运用数据库编程技术、多线程开发技术、网络通讯技术，以Microsoft Visual Studio 2008作为系统前台应用程序开发工具，Microsoft SQL Server 2005作为后台数据库管理系统，在Windows XP平台下进行开发。本设计的完成主要实现了以下功能：
1.实现了用户注册、登录、聊天（加密）、服务器管理等功能
2.支持多用户同时通信
3.支持点对点的文件传输，语音传输
通过程序反复的测试和运行，本设计安全可靠，完成了本局域网聊天软件的设计要求。
关键词：局域网；聊天软件；C#；UDP协议
Abstract:Now,the local area network has been widely integrated into people's lives,the schools,businesses have established their own local area network,the communication is essential for people,so it is necessary to have a secure chat software in lan,it is the objective for the design。
The topic of this paper is going to talk about that to design the chat software in lan based on udp. This local area network chat software using the design stream of the software project, using the C# language which is very common and popular, using the object-oriented approach, the technology of the database programming, multi-threading development technology and the network communication technology, makes Microsoft Visual Studio 2008 as the front application design tool, Microsoft SQL Server 2005 are used as the background DBMS( the database management system ), and it was programmed in the Windows XP System. The completion of the design to achieve the following main features：
1.Implemented user registration,login,chat(encryption),server management and other functions.
2.Communications from multiple users simutaneously.
3.Support point to point filetransfer,voice transmission.
Through the process of repeated tseting and operation,the design is safety and reliable,completed the design requirements for the lan chat software.
Key Words: Local Area Network; Chat Software; C#; UDP protocol
