UWP DatagramSocket组播

Question

我设法制作了一个简单的应用程序，用于从多播组发送和接收数据。如果我打开应用程序的2个实例（2个不同的.sln文件使用相同的代码），我可以发送和接收数据。问题是，5秒后，如果我从Client001发送消息，则只有Client001才会收到消息。但是，如果我在5秒内从Client002（应用程序的第二个实例）发送消息，那么他们都会收到消息。 我有一个UdpClient的例子，它运行得很好，但UWP不再可用了。 总而言之，我怎样才能实现，无论何时（不是在5秒内）某些客户端发送消息，所有其他客户端都能获得它？

这是 MainPage.xaml.cs

的代码

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's 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 + "\"";
            });
        }
    }
}

这是 MainPage.xaml

的代码

<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>

更新：经过一番搜索，我发现可能是TTL（生存时间）问题，但我仍然不知道如何解决这个问题。

Answer 1

  

总而言之，我怎样才能实现，无论何时（不是在5秒内）某些客户端发送消息，所有其他客户端都能获得它？

似乎这个问题已在最新的Windows RS1（Build 14393）操作系统中得到修复，这里是截图（Gif）：

您可能需要升级操作系统才能解决问题。