本程序提供注册功能，并将注册所得用户名密码写入文件，其中用户名与密码只能由英文字母与数字组成。-This procedure provides registration functionality, and user password registered to write the file from which the user name and password only by letters and numbers.

有简单的用户注册，登录，聊天，文件传输，等功能。-There are simple user registration, login, chat, file transfer, and other functions.