Greg Scott from the Windows CE Networking team has posted an interesting article on how Bluetooth Virtual COM ports are implemented on Windows CE.
Alongside the native code to setup a port, there are some details on the improvements in Windows Mobile 5.0 which now includes UI options to set both incoming and outgoing ports and is integrated into the bonding/pairing process. This means that OEMs no longer need to produce their own individual applets to expose this functionality.
For managed code the Bluetooth.NET library wraps this functionality with the BluetoothSerialPort class.
In The Hand Ltd 
2 replies on “Bluetooth COM Ports On Windows CE”
Dear Sir,
I am working on yhe project of bluetooth chat on window XP on VB.Net and i am facing problem when i run it is "An unhandled exception of type ‘System.Net.Sockets.SocketException’ occurred in system.dll
Additional information: An address incompatible with the requested protocol was used"
Please give me the solution if you have any and give me complete description about it.
Thanks
Shahzad Abdul Majeed
This error occurs if the device you are running on doesn’t have Winsock extensions for Bluetooth – the library only supports the Microsoft stack, other stacks have different programming interfaces
Peter