c# - Windows 应用商店应用程序 (.NET) 上的 SSDP (UDP)

Question

我正在尝试使用 C# Windows 应用商店 应用程序实现基本的 SSDP (UDP) 广播/监听器 em>.

我发现 Windows.Networking.Sockets包含 DatagramSocket这是我需要用于 UDP 网络的类。

但是，我目前的尝试似乎执行得很好，但通过 Wireshark 没有结果，也没有从网络上的设备获得响应。

这是我目前正在使用的代码(并通过 RT 模拟器运行):

public async static Task<IEnumerable<HueBridge>> DiscoverAsync(TimeSpan timeout)
{
  if (timeout <= TimeSpan.Zero)
    throw new ArgumentException("Timeout value must be greater than zero.", "timeout");

  var discoveredBridges = new List<HueBridge>();

  using (var socket = new DatagramSocket())
  {
    while (true)
    {
      var bridgeWasFound = false;

      socket.MessageReceived += (sender, e) =>
      {
        var bpx = true; // breakpoint here for success
      };

      var multicastIP = new HostName("239.255.255.250");
      await socket.BindServiceNameAsync("1900");
      socket.JoinMulticastGroup(multicastIP);

      using (var writer = new DataWriter(socket.OutputStream))
      {
        var request = new StringBuilder();
        request.AppendLine("M-SEARCH * HTTP/1.1");
        request.AppendLine("HOST: 239.255.255.250:1900");
        request.AppendLine("MAN: ssdp:discover");
        request.AppendLine("MX: 5");
        request.AppendLine("ST: ssdp:all");

        writer.WriteString(request.ToString());
        await writer.FlushAsync();
      }

      if (timeout > TimeSpan.Zero)
        await Task.Delay(timeout);

      if (!bridgeWasFound)
        break; // breakpoint here for failure check
    }
  }

  return discoveredBridges;
}

关于我可能做错了什么的任何想法？我没有遇到异常，而且我在 list 中设置了正确的功能。我的断点在 break总是被击中，我使用 10 秒的超时。

Answer 1

看来我找到了问题。

首先，我应该使用 socket.BindEndpointAsync(null, string.Empty) 而不是 socket.BindServiceNameAsync("1900")，它将正确监听广播数据包.

其次，writer.FlushAsync() 不写入套接字；但是，writer.StoreAsync() 可以。

这是最终结果，它确实(几乎)完美地工作:

public async static Task<IEnumerable<HueBridge>> DiscoverAsync(TimeSpan timeout)
{
  if (timeout <= TimeSpan.Zero)
    throw new ArgumentException("Timeout value must be greater than zero.", "timeout");

  var discoveredBridges = new List<HueBridge>();
  var multicastIP = new HostName("239.255.255.250");
  var bridgeWasFound = false;

  using (var socket = new DatagramSocket())
  {
    socket.MessageReceived += (sender, e) =>
    {
      var reader = e.GetDataReader();
      var bytesRemaining = reader.UnconsumedBufferLength;
      var receivedString = reader.ReadString(bytesRemaining);

      // TODO: Check for existing bridges, only add new ones to prevent infinite loop.
      // TODO: Create new bridge and add to the list. 

      bridgeWasFound = true;
    };

    await socket.BindEndpointAsync(null, string.Empty);
    socket.JoinMulticastGroup(multicastIP);

    while (true)
    {
      bridgeWasFound = false;

      using (var stream = await socket.GetOutputStreamAsync(multicastIP, "1900"))
      using (var writer = new DataWriter(stream))
      {
        var request = new StringBuilder();
        request.AppendLine("M-SEARCH * HTTP/1.1");
        request.AppendLine("HOST: 239.255.255.250:1900");
        request.AppendLine("MAN: ssdp:discover");
        request.AppendLine("MX: 3");
        request.AppendLine("ST: ssdp:all");

        writer.WriteString(request.ToString());
        await writer.StoreAsync();

        if (timeout > TimeSpan.Zero)
          await Task.Delay(timeout);

        if (!bridgeWasFound)
          break;
      }
    }
  }

  return discoveredBridges;
}