这是一个用于双工控制的类，需配合自己的网络代码，重要的是其中的切换逻辑-This is a duplex control for the class, need to meet their networking code, it is important to the switching logic

该代码在FB中提供桥接功能,不过他只是在以太网接口上工作,能提供多个逻辑桥-FB provide bridging function, but he is in Ethernet interface, logic can provide a number of bridge