Agent.cs

            UdpClient client = new UdpClient(9); // UdpClient that listens to port 9
            IPEndPoint endPoint = new IPEndPoint(IPAddress.Any, 0); // Receive from any IP
            TcpClient answerer;
            byte[] received;
            byte[] answerNonMagicPacket = Encoding.UTF8.GetBytes("WolUtilities");
            byte[] answerMagicPacket = Encoding.UTF8.GetBytes("ShuttingDown");
            string mac = GetMachineMacAddress();

            Console.WriteLine("Listening to magic packets... MAC address of this machine is: {0}", mac);

            while (true)
            {
                received = client.Receive(ref endPoint); // Blocks until message is got

                if (IsMagicPacket(received, mac))
                {
                    Console.WriteLine($"Received a magic packet from {endPoint.Address}:{endPoint.Port}, answering.");
                    using (answerer = new TcpClient(endPoint.Address.ToString(), endPoint.Port))
                    {
                        NetworkStream stream = answerer.GetStream();
                        stream.Write(answerMagicPacket, 0, answerMagicPacket.Length);
                    }
                }
                else
                {
                    Console.WriteLine($"Received a non-magic packet from {endPoint.Address}:{endPoint.Port}, answering.");
                    using (answerer = new TcpClient(endPoint.Address.ToString(), endPoint.Port))
                    {
                        NetworkStream stream = answerer.GetStream();
                        stream.Write(answerNonMagicPacket, 0, answerNonMagicPacket.Length);
                    }
                }
            }

Program.cs
Console.WriteLine("Hello, World!\nSending Wol packet");
WakeOnLan wol = new WakeOnLan("IP", Port, "MacAddress");

wol.Send();
IPEndPoint endPoint = new IPEndPoint(IPAddress.Any, 0); // Receive from any IP
TcpListener listener = null;

try
{
    listener = new TcpListener(IPAddress.Parse("127.0.0.1"), 9);
    listener.Start();

    byte[] received = new byte[512];
    string data;

    using (TcpClient client = listener.AcceptTcpClient())
    {
        Console.WriteLine("Answerer connected!");

        NetworkStream stream = client.GetStream();

        int i;

        while ((i = stream.Read(received, 0, received.Length)) != 0)
        {
            // Translate data bytes to a UTF8 string.
            data = Encoding.UTF8.GetString(received, 0, i);
            Console.WriteLine("Received: {0}", data);

            if (data == "WolUtilities")
            {
                Console.WriteLine("The client received a non-magic packet, success.");
                break;
            }
            else if (data == "ShuttingDown")
            {
                Console.WriteLine("The client received a magic-packet, success.");
                break;
            }
            else
            {
                Console.WriteLine(data);
                Console.WriteLine("I don't know what to do with that :(");
            }

        }
    }
}
catch (Exception ex)
{
    Console.WriteLine($"{ex.GetType()}: {ex.Message}");
}
finally
{
    Console.ReadLine();
}