Abstract: a LAN chat software, with less resource consumption and easy to use and flexible, is designed by use of peer-to-peer mode and VC + +6.0 and UDP protocol. In the software communication process, the status of the user is equal. The chat communication portion of the software based on asynchronous socket SOCKET programming, greatly reduces the consumption of system resources, and improves communication efficiency. The file transfer part of the software uses multi-threaded programming, and is suitable for a large amount of data. At the same time, the software achieves a variety of functions related to “Friends”. The experiments show that: the software is of great practical use.