CODEWITHSUNDEEP
c#socketsuwp
Nestor
Nestor

Reputation: 8384

UDP broadcast send not working in UWP

I tried to create an UDP send and listen application with UWP based on this source code.

It should work like this:

I have the Listen and Send methods.

Constructor

public MainViewModel()
{
   Listen();
   Send();
}

Listen

private async void Listen()
    {
      listenerSocket = new DatagramSocket();
      listenerSocket.MessageReceived += (x, y) =>
      {
        var a = "2";
      };
      await listenerSocket.BindServiceNameAsync("8080");
    }

Send

private async void Send()
    {
      IOutputStream outputStream;
      string localIPString = GetLocalIp();
      IPAddress localIP = IPAddress.Parse(localIPString);
      string subnetMaskString = "255.0.0.0";
      IPAddress subnetIP = IPAddress.Parse(subnetMaskString); 
      HostName remoteHostname = new HostName(GetBroadcastAddress(localIP, subnetIP).ToString());
      outputStream = await listenerSocket.GetOutputStreamAsync(remoteHostname, "8080");      
      DataWriter writer = new DataWriter(outputStream);
      writer.WriteString(localIPString);
      await writer.StoreAsync();
    }

It seems that the broadcast sending is not working.

I have another program (written in Java) that also sends a message to the broadcast address, and this listener receives the messages sent back from the broadcast.

What should I set to make the sending work?

Upvotes: 2

Views: 3544

Answers (1)

panda
panda

Reputation: 560

i didn't see any GetBroadcastAddress(localIP, subnetIP) code here. But as I see, your problem may be with this code:

HostName remoteHostname = new HostName(GetBroadcastAddress(localIP, subnetIP).ToString());

I changed it to:

    HostName remoteHostname = new HostName(localIP.ToString());
    outputStream = await listenerSocket.GetOutputStreamAsync(remoteHostname, port);

Here is my sample code:

public sealed partial class MainPage : Page
{
    DatagramSocket listenerSocket = null;
    const string port = "8080";
    public MainPage()
    {
        this.InitializeComponent();
        Listen();
        Send();
    }


private async void Listen()
{
    listenerSocket = new DatagramSocket();
    //listenerSocket.MessageReceived += (x, y) =>
    //{
    //    var a = "2";
    //};
    listenerSocket.MessageReceived += MessageReceived;
    await listenerSocket.BindServiceNameAsync(port);
}

private async void Send()
{
    IOutputStream outputStream;
    string localIPString = GetLocalIp();
    IPAddress localIP = IPAddress.Parse(localIPString);
    string subnetMaskString = "255.0.0.0";
    IPAddress subnetIP = IPAddress.Parse(subnetMaskString);
    HostName remoteHostname = new HostName(localIP.ToString());
    outputStream = await listenerSocket.GetOutputStreamAsync(remoteHostname, port);

    using (DataWriter writer = new DataWriter(outputStream))
    {
        writer.WriteString("aaaa");
        await writer.StoreAsync();
    }


}

//private object GetBroadcastAddress(IPAddress localIP, IPAddress subnetIP)
//{
//    throw new NotImplementedException();
//}

async void MessageReceived (DatagramSocket socket, DatagramSocketMessageReceivedEventArgs args)
{
    DataReader reader = args.GetDataReader();
    uint len = reader.UnconsumedBufferLength;
    string msg = reader.ReadString(len);

    string remoteHost = args.RemoteAddress.DisplayName;
    reader.Dispose();

    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        text.Text = msg;
    });

}

private string GetLocalIp()
{
   ...
}

}

Upvotes: 2

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