using System;

using System.Net;

using System.Net.Sockets;

using System.Threading.Tasks;

using System.Text;

​

public class Program

{

    public static void Main()

    {

        int PORT = 9876;

UdpClient udpClient = new UdpClient();

udpClient.Client.Bind(new IPEndPoint(IPAddress.Any, PORT));

​

var from = new IPEndPoint(0, 0);

Task.Run(() =>

{

    while (true)

    {

        var recvBuffer = udpClient.Receive(ref from);

        Console.WriteLine(Encoding.UTF8.GetString(recvBuffer));

    }

});

​

var data = Encoding.UTF8.GetBytes("ABCD");

udpClient.Send(data, data.Length, "255.255.255.255", PORT);

    }

}