tcp文件服务器和客户点，客户端可以上传和下载，支持一些命令help：显示客户端所有命令和说，明，list：显示下载列表，get：下载，put：上传，quit：退出。-tcp file servers and clients point, the client can upload and download, support some command help: Shows all the commands and the client said that, list: show downloa