UWP DatagramSocket Multicast

Question

I managed to create a simple application that sends and receives data from a multicast group. If I open 2 instances of the application (2 different .sln files with the same code), I can send and receive data. The problem is that after 5 seconds, if I send a message with Client001, only the message Client001 will receive the message. But, if I send a message with Client002 (the second instance of the application) within 5 seconds, then both of them will receive the message. I had an example with UdpClient that worked fine, but it is no longer available for UWP. So in conclusion, how can I achieve, no matter when (not within 5 seconds) some of the clients send a message, all the other clients receive it?

This is the code for MainPage.xaml.cs

namespace Client001
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        private DatagramSocket listenerSocket = null;
        public string remoteAddress = "224.3.0.5";
        HostName remoteHostname;
        public string serviceName = "22113";
        IOutputStream outputStream;
        DataWriter writer;

        public MainPage()
        {
            this.InitializeComponent();
            SetupMulticastScenarioUI();

            remoteHostname = new HostName(RemoteAddress.Text);
        }

        private void CloseListenerSocket()
        {
            if (listenerSocket != null)
            {
                // DatagramSocket.Close() is exposed through the Dispose() method in C#.
                // The call below explicitly closes the socket, freeing the UDP port that it is currently bound to.
                listenerSocket.Dispose();
                listenerSocket = null;
            }
        }

        // Sets up the UI to display the multicast scenario options.
        private void SetupMulticastScenarioUI()
        {
            RemoteAddress.Text = remoteAddress;
            ServiceName.Text = serviceName;
            StartListener.Content = "Start listener and join multicast group";
            SendMessageButton.IsEnabled = false;
            CloseListenerButton.IsEnabled = false;
            SendOutput.Text = "";
        }

        private async void StartListener_Click(object sender, RoutedEventArgs e)
        {
            listenerSocket = new DatagramSocket();

            listenerSocket.Control.MulticastOnly = true;
            await listenerSocket.BindServiceNameAsync(ServiceName.Text);

            // Join the multicast group to start receiving datagrams being sent to that group.
            listenerSocket.JoinMulticastGroup(remoteHostname);

            listenerSocket.MessageReceived += MessageReceived;
            SendOutput.Text = "Listening on port " + listenerSocket.Information.LocalPort + " and joined to multicast group";

            // Enable scenario steps that require us to have an active listening socket.
            SendMessageButton.IsEnabled = true;
            CloseListenerButton.IsEnabled = true;

            outputStream = await listenerSocket.GetOutputStreamAsync(remoteHostname, ServiceName.Text);
            writer = new DataWriter(outputStream);
            writer.WriteString("Handshake1");
            await writer.StoreAsync();
        }

        private async void SendMessage_Click(object sender, RoutedEventArgs e)
        {
            writer.WriteString(Message.Text);
            await writer.StoreAsync();
        }

        private void CloseListener_Click(object sender, RoutedEventArgs e)
        {
            CloseListenerSocket();

            // Disable scenario steps that require us to have an active listening socket.
            SendMessageButton.IsEnabled = false;
            CloseListenerButton.IsEnabled = false;
            SendOutput.Text = "";

            SendOutput.Text = "Listener closed";
        }

        async void MessageReceived(DatagramSocket socket, DatagramSocketMessageReceivedEventArgs eventArguments)
        {
            // Interpret the incoming datagram entire contents as a string.
            uint stringLength = eventArguments.GetDataReader().UnconsumedBufferLength;
            string receivedMessage = eventArguments.GetDataReader().ReadString(stringLength);

            await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                SendOutput.Text = "Received data from remote peer (Remote Address: " +
                    eventArguments.RemoteAddress.CanonicalName + ", Remote Port: " +
                    eventArguments.RemotePort + "): \"" + receivedMessage + "\"";
            });
        }
    }
}

MainPage.xaml

<Page
    x:Class="Client001.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Client001"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">


    <StackPanel>
        <TextBlock>Remote Address:</TextBlock>
        <TextBox x:Name="RemoteAddress" />

        <TextBlock>Service Name:</TextBlock>
        <TextBox x:Name="ServiceName" />

        <Button x:Name="StartListener" Click="StartListener_Click" Margin="0,10,0,0"/>
        <Button x:Name="SendMessageButton" Content="Send 'hello'" Click="SendMessage_Click" Margin="0,10,0,0"/>
        <Button x:Name="CloseListenerButton" Content="Close Listener" Click="CloseListener_Click" Margin="0,10,0,0"/>
        <TextBlock x:Name="SendOutput" TextWrapping="Wrap"  Margin="0,10,0,0"/>
        <TextBox x:Name="Message"></TextBox>
    </StackPanel>

</Page>

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Answer 1

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, ​​ Windows RS1 (Build 14393), (Gif):

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