C#

namespace PortForwarder
{
    class Program
    {
        public static UdpClient UDP1 = new UdpClient(7777);

        static void Main(string[] args)
        {
            Console.Title = "Port Forwarder";
            Console.WriteLine("-= Port Forwarder started. =-");
            Console.WriteLine("UDP port 7777 forwarded");

            UDP1.BeginReceive(ReceiveDataUDP1, null);

            while (true) { };
        }

        static void ReceiveDataUDP1(IAsyncResult ar)
        {
            IPEndPoint IEP = new IPEndPoint(IPAddress.Any, 0);
            Byte[] receiveBytes = UDP1.EndReceive(ar, ref IEP);

	    // Trying to "lie" about local IEP results in exception
            // UdpClient US1 = new UdpClient(IEP);
            // US1.Send(receiveBytes, receiveBytes.Length, "192.168.0.2", 7777);

	    UDP1.Send(receiveBytes, receiveBytes.Length, "192.168.0.2", 7777);
            UDP1.BeginReceive(ReceiveDataUDP1, null);
        }
    }
}