I have been trying to write a VB program to use Bluetooth to
communicate between a PDA running Windows CE 4.2 and another BT
device.  I found this article that got me started:
http://www.devx.com/wireless/Article/11511

Using the technique in this article, I can successfully transmit data
but the receive part fails.  In fact it slows the PDA to a crawl.
Does anyone have any ideas on how to modify the original program so
that the receive function will work?

BTW, I am using VS 2005 and the original program was for an earlier
version of VS.  I am not sure if this is relevant.

Here is the relevant section of the source from the article:

   Dim infileHandler As Long
   Dim outfileHandler As Long
   Dim numReadWrite As Integer
   Dim t1 As System.Threading.Thread
   Dim stopThread As Boolean = False

   Public Sub connect()
       '---port number for Bluetooth connection
       Dim inPort As Short = 8
       Dim outPort As Short = 6

       '---Opens the port for Bluetooth
       infileHandler = CreateFile("COM" & inPort & ":", _
                                   &HC0000000, 0, 0, 3, 0, 0)
       Application.DoEvents()
       outfileHandler = CreateFile("COM" & outPort & ":", _
                                   &HC0000000, 0, 0, 3, 0, 0)
       Application.DoEvents()

       '---invoke the thread to receive incoming messages
       stopThread = False
       t1 = New Threading.Thread(AddressOf receiveLoop)
       t1.Start()
   End Sub

   Public Sub disconnect()
       stopThread = True
       CloseHandle(infileHandler)
       CloseHandle(outfileHandler)
   End Sub

  <DllImport("coredll.dll")> _
   Private Shared Function CreateFile(ByVal lpFileName As String, _
                                      ByVal dwDesiredAccess As
Integer, _
                                      ByVal dwShareMode As Integer, _
                                      ByVal lpSecurityAttributes As
Integer, _
                                      ByVal dwCreationDisposition As
Integer, _
                                      ByVal dwFlagsAndAttributes As
Integer, _
                                      ByVal hTemplateFile As Integer)
As Integer
   End Function

   <DllImport("coredll.dll")> _
  Private Shared Function ReadFile(ByVal hFile As Integer, _
                                   ByVal Buffer() As Byte, _
                                   ByVal nNumberOfBytesToRead As
Integer, _
                                   ByRef lpNumberOfBytesRead As
Integer, _
                                   ByRef lpOverlapped As Integer) As
Integer
   End Function

   <DllImport("coredll.dll")> _
   Private Shared Function WriteFile(ByVal hFile As Integer, _
                                     ByVal Buffer() As Byte, _
                                     ByVal nNumberOfBytesToWrite As
Integer, _
                                     ByRef lpNumberOfBytesWritten As
Integer, _
                                     ByVal lpOverlapped As Integer)
As Boolean
   End Function

   <DllImport("coredll.dll")> _
   Private Shared Function CloseHandle(ByVal hObject As Integer) As
Integer
   End Function

   Public Function send(ByVal message As String) As Integer
       '---send the message through the serial port
       Dim value As String = message & vbCrLf
       Dim retCode As Integer = WriteFile(outfileHandler, _
                                          stringToByteArray(value), _
                                          value.Length(), _
                                          numReadWrite, _
                                          0)
       txtMessageLog.Text += value
       Return retCode
   End Function

   Public Sub receiveLoop()
       '---receive the message through the serial port
       Dim inbuff(300) As Byte
       Dim retCode As Integer = ReadFile(infileHandler, _
                                         inbuff, _
                                         inbuff.Length, _
                                         numReadWrite, _
                                         0)
       Application.DoEvents()
       While True
           If retCode = 0 Or stopThread Then
               'MsgBox("Error reading message.")
               Exit While
           Else
               Dim updateDelegate As New _
                   myDelegate(AddressOf updateMessageLog)

               updateDelegate.Invoke(byteArrayToString(inbuff))
               ReDim inbuff(300)
               retCode = ReadFile(infileHandler, _
                                  inbuff, _
                                  inbuff.Length, _
                                  numReadWrite, _
                                  0)
               Application.DoEvents()
           End If
       End While
   End Sub

   Public Delegate Sub myDelegate(ByVal str As String)

   Public Sub updateMessageLog(ByVal str As String)
       If str.Length > 0 Then
           txtMessageLog.Text += "-->" & str
       End If
   End Sub

The only thing I had to change was the port numbers to match the BT
COM ports on my PDA.  The Text box for receiving the incoming stream
immediately becomes filled with repeated instances of -->, as
updateMessageLog is apparently called repeatedly.  I hope that there
is a simple solution to this problem.