code:

using System;
using System.Net;
using System.Net.Sockets;

namespace UdpTest
{
  class Program
  {
    static DateTime lastTime = DateTime.Now;
    static TimeSpan maxSpan = TimeSpan.FromSeconds(0);

    static void UpdAsyncCallback(IAsyncResult iar)
    {
      UdpClient client = iar.AsyncState as UdpClient;
      try
      {
        IPEndPoint e = new IPEndPoint(IPAddress.Any, 0);
        var data = client.EndReceive(iar, ref e);

        if (e.Address.Equals(IPAddress.Parse("10.104.128.105")))
        {
          DateTime now = DateTime.Now;
          TimeSpan span = now.Subtract(lastTime);
          Console.WriteLine("{0} delta {1} length {2}", e.Address, span, data.Length);
          if (span > maxSpan)
          {
            Console.WriteLine("  new span {0}", span);
            maxSpan = span;
          }
          lastTime = now;
        }
      }
      catch (Exception ex)
      {
        Console.WriteLine("UpdAsyncCallback error {0}", ex.Message);
      }
      client.BeginReceive(UpdAsyncCallback, client);
    }


    static void Main(string[] args)
    {
      try
      {
        var udpClient = new UdpClient();
        udpClient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
        udpClient.Client.Bind(new IPEndPoint(IPAddress.Any, 2467));
        udpClient.JoinMulticastGroup(IPAddress.Parse("224.0.23.175"));
        udpClient.BeginReceive(UpdAsyncCallback, udpClient);
        while (true) System.Threading.Thread.Sleep(1000);
      }
      catch (Exception ex)
      {
        Console.WriteLine(ex.Message);
      }
    }
  }
}