C# Resolve Gateway MAC from public ip addr. Thanks to Stackoverflow community

Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace Arp
{
    class Program
    {
        static void Main(string[] args)
        {
            var client = new WebClient();

            var ipAddress = client.DownloadString("http://ipecho.net/plain");
            IPAddress address = IPAddress.Parse(ipAddress);
            byte[] t = GetMacAddress(address);
            string mac = string.Join(":", (from z in t select z.ToString("X2")).ToArray());

            Console.WriteLine(mac);

  
            Console.ReadLine();
        }

        [DllImport("iphlpapi.dll", ExactSpelling = true)]
        public static extern int SendARP(uint destIP, uint srcIP, byte[] macAddress, ref uint macAddressLength);

        public static byte[] GetMacAddress(IPAddress address)
        {
            byte[] mac = new byte[6];
            uint len = (uint)mac.Length;
            byte[] addressBytes = address.GetAddressBytes();
            uint dest = ((uint)addressBytes[3] << 24)
              + ((uint)addressBytes[2] << 16)
              + ((uint)addressBytes[1] << 8)
              + ((uint)addressBytes[0]);
            if (SendARP(dest, 0, mac, ref len) != 0)
            {
                throw new Exception("The ARP request failed.");
            }
            return mac;
        }
    }
}