Widcomm bluetooth : how to open the virtual COM

Question

Hi! i'm trying to use the Widcomm bluetooth stack by Broadcomm and it should work but there's one thing that still i cannot understand: HOW CAN I AUTOMATICALLY OPEN THE VIRTUAL COM WHEN I NEED TO COMMUNICATE?

i am trying to use SPP (Serial Port Profile) but the documentation with the SDK is not so exaustive.

PLEASE, I JUST CANNOT USE 32FEET!

I wrapped the SPP Server part of the API:

    [DllImport("wcbts.dll", SetLastError = false, CharSet = CharSet.Unicode)]
    internal static extern IntPtr CreateSppServer(IntPtr pStack);

    [DllImport("wcbts.dll", SetLastError = false, CharSet = CharSet.Unicode)]
    internal static extern void DeleteSppServer(IntPtr pServer);

    [DllImport("wcbts.dll", SetLastError = false, CharSet = CharSet.Unicode)]
    internal static extern bool SppServerStart(IntPtr pServer, IntPtr pszServiceName);

    [DllImport("wcbts.dll", SetLastError = false, CharSet = CharSet.Unicode)]
    internal static extern bool SppServerStop(IntPtr pServer);

    [DllImport("wcbts.dll", SetLastError = false, CharSet = CharSet.Unicode)]
    internal static extern IntPtr SppServerNotifyWindow(IntPtr pServer, IntPtr hWnd, int nMsg);

What is pszServiceName? where i can find it? and hWnd and nMsg???

Thanks

Answer 1

So first off you say you can't use 32feet.net. Why? You're obviously using João Paulo Figueira's bluetooth stack library, because that's what wcbts.dll is, so it can't be some mandate against using some 3rd party library (and 32feet is free and open source).

That brings me to question #2. If you're using his library, have you looked at his sample on how to use that library? It's downloaded from the same place as the DLL you must have.

As for what hWnd and nMsg are, just based on the fact this is Windows programming and the name of the API, I'd say hWnd is the handle of the window that will get notifications when something happens in the library and nMsg is whatever custom message constant you want passed to that window so you would be able to look for those messages. Again, I'm betting the sample he provides shows all of this.

Answer 2

I posted a response to this earlier but it seems never to have appeared! :-(

Anyway, I'm the maintainer of the 32feet.NET library and the author of the Widcomm support. Firstly, as far as I know the license should not be a problem for commercial distribution. See Peter Foot's comment at http://32feet.net/forums/t/2289.aspx:

"32feet.NET is free for commercial or non-commercial use. If you use the binaries you can just use the library as-is, if you make modifications to the source you need to include the 32feet.NET License.txt document and ensure the file headers are not modified/removed."

I'll see if Peter can post a comment here to give certainty.

Anyway, we haven't implemented support for the Widcomm virtual COM port functionality, (its certainly possible though no one has asked for it -- apart from yourself). I'm not a big fan of virtual COM ports. It always seems much easier to use a direct 'sockets' connection, rather than attempt to setup a COM port, and try to find what name it was created as[1], and then have to open a SerialPort to use it, and then if the connection is lost one doesn't know and have simply to keep retrying... Its so much easier just to do the following:

Dim addr As BluetoothAddress _
  = BluetoothAddress.Parse("001122334455")
'
Dim ep As New BluetoothEndPoint(addr, BluetoothService.SerialPort)
Dim cli As New BluetoothClient
cli.Connect(ep)
Dim peerStream As Stream = cli.GetStream()
peerStream.Write/Read ...

See more at http://www.alanjmcf.me.uk/comms/bluetooth/32feet.NET%20--%20User%20Guide.html

To answer your specific Widcomm questions. Multiple instances of a Bluetooth service can be created, i.e. multiple SPP services (each using the SPP Service Class Id), each can supply a Service Name attribute to allow clients to select between them. In most cases it won't be necessary, so just pass null or zero-length string -- the Widcomm SDK docs don't say what's allowed. As to the Window handles, Widcomm uses C++ virtual methods (yuk -- this makes direct P/Invoking mostly impossible) to implement events/callbacks, presumably Mr Figueira's code converts those callbacks into Window messages.

[1] Creating Bluetooth virtual COM ports is not straightforward. On MSFT+Win32, one isn't told what name was selected for the COM port! On MSFT+WM the official API doesn't work well on many device types. And our unofficial method of doing it requires a reboot IIRC. :-(