扫描局域网中哪些主机正在联网 并获取其MAC地址 可以很方便的设定扫描IP的范围 （注释很详细 ） 在学校局域网中实验效果很好-Scan local area network in which the host is Network and to obtain its MAC address can be easily configured to scan the IP range (Note very carefully) experiment in the school local