internal UdpClient Listener;
...
IPEndPoint rep = new IPEndPoint(IPAddress.Parse("0.0.0.0"), 1);
...
packege = Listener.Receive(ref rep);

UdpClient Cl;
        int Count = 1;
        private void Button_Click_3(object sender, RoutedEventArgs e)
        {

            Cl = new UdpClient(new IPEndPoint(IPAddress.Any, 1002));
            Cl.AllowNatTraversal(true);

        }

        private void Button_Click_4(object sender, RoutedEventArgs e)
        {

            byte[] s = new byte[1];
            s[0] = (byte)Count;
            Cl.Send(s, s.Length, new IPEndPoint(IPAddress.Parse("127.0.0.1"), 1002));
            
        }

        private void Button_Click_5(object sender, RoutedEventArgs e)
        {
            IPEndPoint rep = new IPEndPoint(IPAddress.Parse("0.0.0.0"), 1);
            byte[] packege; 
            packege = Cl.Receive(ref rep);
            MessageBox.Show(packege.Length.ToString());
            
            
        }