北大青鸟一单元项目。Java实现socket变成。完成一个客户端和服务器交互应用。实现主要功能，库存管理，前台收银，会员管理。会员打折等功能！-Beida Jade Bird a unit project. Java implementation of socket programming. A complete client and server interaction applications. To achieve the main functions, inventory managem