ClienteUDP

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

namespace ClientUDP
{
    class Cliente
    {
        static void Main(string[] args)
        {
            Client();
        }
        static void Client()
        {
            byte[] data = new byte[1024]; // Tamaño de la data
            IPEndPoint ip = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9999); // seteamos la ip y el puerto de escucha

            Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp); // Creamos un objeto del tipo socket UDP

            string welcome = "Hello Server"; // string a enviar.
            data = Encoding.ASCII.GetBytes(welcome); // codificamos el string
            server.SendTo(data, data.Length, SocketFlags.None, ip); // enviamos la data, el tamaño, un flags none y la ip

            IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
            EndPoint Remote = (EndPoint)sender;

            data = new byte[1024];
            int receivedDataLength = server.ReceiveFrom(data, ref Remote);

            Console.WriteLine("Message received from {0}:", Remote.ToString());
            Console.WriteLine(Encoding.ASCII.GetString(data, 0, receivedDataLength));
            Console.Read();
            server.Close();
        }

    }
}