提供服务端登陆验证程序（验证码随机改变，防止非法进入）； 提供服务器控制程序，管理员可以允许、屏蔽和删除一个注册用户的登陆客户端； 任何改变访问地点的行为，都必须得到管理员的授权，否则无法登陆系统； 即使知道其他用户的密码也不能登陆系统。-provide certification services-landing procedures (Random Verification code change to prevent illegal entry); Provide ser

For developers who design and program devices that use the USB interface. Introduce the USB and help to get your devices and communicating as quickly and easily as possible.The USB is versatile enough for a wide range of peripheral devices. Standar