这个是Delphi 2007下写的，需要Indy的ICMP控件 (Delphi2006应该也能编译，因为都带的是Indy10)

原理就是多线程Ping一个网关下的所有主机，然后导出ARP缓存。

因为Ping前会发出ARP请求获取每个IP的MAC地址，所以在Ping完后用 arp -a 取得本机ARP缓存。

最后就是读入arp -a 的返回，并存起来备查。-This is written under Delphi 2007 and need to Indy the ICMP control (Delphi2006 should be able to compile, because both bands are Indy10) principle is a multi-threaded gateway Ping all hosts, and then export the ARP cache. Ping will be issued because the previous ARP request to obtain the MAC address for each IP, so after Ping using arp-a to obtain the local ARP cache. Finally is read into the arp-a return, both up for future reference.