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I want to create a two-way Bluetooth Rfcomm connection. The server side is implemented in UWP. Using InTheHand.Devices.Bluetooth (NuGet v4.0.1803.22-preview) I find no way to attach an SDP record to the service provider. This results in an error when trying to advertise the service.

I suppose one could cast the 'InTheHand' service provider to the Windows.Devices.Bluetooth.Rfcomm variety, but I'd prefer a solution within the InTheHand library if possible. Am I missing something?

private async void InitializeService(){
    var localRfcommServiceID = RfcommServiceId.FromUuid(uuid);
    var localRfcommService = await RfcommServiceProvider.CreateAsync(localRfcommServiceID);

//This is where I would expect to add SDP records to the service provider

    localRfcommService.StartAdvertising();
    localRfcommService.ConnectionReceived += LocalRfcommService_ConnectionReceived;
}

I get an exception when I try to start advertising. (Sorry for German error messages) 

Exception thrown: 'System.IO.FileNotFoundException' in InTheHand.Devices.Bluetooth.dll
WinRT information: Der StreamSocketListener muss gebunden werden, bevor Sie mit der Ankündigung beginnen können.
Exception thrown: 'System.IO.FileNotFoundException' in System.Private.CoreLib.ni.dll
WinRT information: Der StreamSocketListener muss gebunden werden, bevor Sie mit der Ankündigung beginnen können.

Translated: The StreamSocketListener needs to be bound before advertising can begin.

ChrisM
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  • Hi, Did you add a `StreamSocketListener` as indicated by the error message? – Richard Zhang Aug 16 '19 at 09:57
  • So far I've cast the provider to the Windows variety and bound it to a StreamSocketLiestener as I can find no obvious way of binding it in the InTheHand library. Seems to be working; still trying to discover it client-side though. – ChrisM Aug 19 '19 at 10:43

1 Answers1

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I ended up casting the 'InTheHand' RfcommServiceProvider to a 'Windows.Devices.Bluetooth.Rfcomm.RfcommServiceProvider', then binding the service name to it and initializing the SDP attributes. 

async void InitializeService()
{
    var localRfcommProvider = await RfcommServiceProvider.CreateAsync(Constants.RfcommServiceUuid);
    var rfcommServiceID = RfcommServiceId.FromUuid(Constants.RfcommServiceUuid);
    socketListener = new StreamSocketListener();
    socketListener.ConnectionReceived += SocketListener_ConnectionReceived;      
    await socketListener.BindServiceNameAsync(rfcommServiceID.AsString(),SocketProtectionLevel.BluetoothEncryptionAllowNullAuthentication);
    InitializeServiceSdpAttributes(localRfcommProvider);

    try
    {
        ((Windows.Devices.Bluetooth.Rfcomm.RfcommServiceProvider)localRfcommProvider).StartAdvertising(socketListener);  
    }
    catch (Exception e)
    {
            Debug.WriteLine(e.Message);
    }
}


void InitializeServiceSdpAttributes(Windows.Devices.Bluetooth.Rfcomm.RfcommServiceProvider provider)
    {
        var sdpWriter = new DataWriter();

        //Write the service name attribute
        sdpWriter.WriteByte(Constants.SdpServiceNameAttributeType);

        // The length of the UTF-8 encoded Service Name SDP Attribute.
        sdpWriter.WriteByte((byte)Constants.SdpServiceName.Length);

        // The UTF-8 encoded Service Name value.
        sdpWriter.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
        sdpWriter.WriteString(Constants.SdpServiceName);

        // Set the SDP Attribute on the RFCOMM Service Provider.
        provider.SdpRawAttributes.Add(Constants.SdpServiceNameAttributeId, sdpWriter.DetachBuffer());
    }

An example of Initializing the SDP attributes was found in Microsoft's UWP samples.

ChrisM
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