using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;

namespace IPtoMacAddress
{
    class IPtoMac
    {
        [System.Runtime.InteropServices.DllImport("Iphlpapi.dll", EntryPoint = "SendARP")]
        internal extern static Int32 SendArp(Int32 destIpAddress, Int32 srcIpAddress, byte[] macAddress, ref Int32 macAddressLength);

        public  PhysicalAddress GetMacFromIP(IPAddress IP)
        {
            if (IP.AddressFamily != AddressFamily.InterNetwork)
                throw new ArgumentException("supports just IPv4 addresses");

            Int32 addrInt = IpToInt(IP);
            Int32 srcAddrInt = 0;
            byte[] mac = new byte[6]; // 48 bit

            int length = mac.Length;
            int reply = SendArp(addrInt, srcAddrInt, mac, ref length);

            byte[] emptyMac = new byte[12];

            if (reply != 0)
            {
                //No MAC Address found for the IP Address
                return new PhysicalAddress(emptyMac);
            }
            return new PhysicalAddress(mac);
        }

        private static Int32 IpToInt(System.Net.IPAddress IP)
        {
            byte[] bytes = IP.GetAddressBytes();
            return BitConverter.ToInt32(bytes, 0);
        }
    }
}