SendArp擷取MAC地址

        [DllImport("Iphlpapi.dll")]
        static extern int SendARP(Int32 DestIP, Int32 SrcIP, ref Int64 MacAddr, ref Int32 PhyAddrLen);

        [DllImport("Ws2_32.dll")]
        static extern Int32 inet_addr(string ipaddr);

        //SendArp擷取MAC地址
        public static string GetMacAddress(string macip)
        {
            StringBuilder strReturn = new StringBuilder();
            try
            {
                Int32 remote = inet_addr(macip);

                Int64 macinfo = new Int64();
                Int32 length = 6;
                SendARP(remote, 0, ref macinfo, ref length);

                string temp = System.Convert.ToString(macinfo, 16).PadLeft(12, '0').ToUpper();

                int x = 12;
                for (int i = 0; i < 6; i++)
                {
                    if (i == 5) { strReturn.Append(temp.Substring(x - 2, 2)); }
                    else { strReturn.Append(temp.Substring(x - 2, 2) + ":"); }
                    x -= 2;
                }

                return strReturn.ToString();
            }
            catch
            {
                return strReturn.ToString();
            }
        }