I am trying to implement a basic SSDP ( UDP ) broadcast/listener for a Windows Store application using C# .
I have found that Windows.Networking.Sockets
contains the DatagramSocket
class which is what I need to use for UDP networking.
However, my current attempts seem to execute just fine but have no results via Wireshark and do not get a response back from the devices on the network.
Here is the code I am currently using (and running through the RT Simulator):
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;
}
Any ideas on what I may be doing incorrectly? I don't get an exception and I have the proper Capabilities set in the manifest. My breakpoint at the break
always gets hit and I am using a timeout of 10 seconds.
Seems I have found the problem(s).
First, I should use socket.BindEndpointAsync(null, string.Empty)
instead of socket.BindServiceNameAsync("1900")
, which will properly listen for broadcast packets.
Secondly, writer.FlushAsync()
does not write to the socket; however, writer.StoreAsync()
does.
Here is the final result, which does work (almost) perfectly:
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;
}
According Specifications :
MAN REQUIRED by HTTP Extension Framework. Unlike the NTS and ST field values, the field value of the MAN header field is enclosed in double quotes; it defines the scope (namespace) of the extension. MUST be "ssdp:discover".
then your code
request.AppendLine("MAN: ssdp:discover");
must be
request.AppendLine("MAN: \"ssdp:discover\"");
Hope this help.
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