WinCE: Failed to open the created bluetooth virtual com port

I am trying to get Bluetooth printer to work on a WinCE handheld. The device is already set as trusted in Control Panel\Bluetooth Device Property, PIN authenticated.

The RegisterDevice call returns a device handle, without error, but when I try to open the port via CreateFileW with OPEN_EXISTING, I got INVALID_HANDLE_VALUE , with system error code 55 ERROR_DEV_NOT_EXIST.

I am very new to WinCE API, new to C++ also. I can't see where the problem is.

What's wrong with my settings? Is there any extra steps to take before I can talk to the printer over this bt-vcom ?

My device is a WM5 HTC Diamond Phone. in its Communication Manager>Bluetooth>COM Port section, I can't see any of the port I created (but they seems indeed created: listed in 3rd party app e.g. TerminalCE, and reported as occupied when trying to create virtual com port in system GUI with these port.). If I create a different Outgoing Port in the system GUI here, Python can talk to the printer progrogramatically via the new port. Am not I using the same API after all... why mine not working ?

My code is adapted from https://msdn.microsoft.com/en-us/library/ms881004.aspx as follows:

# -*- coding: utf-8 -*-
from time import sleep
import ctypes
from ctypes import POINTER, Structure
from ctypes import c_ulonglong, c_int, pointer, c_ulong, c_wchar, c_char, c_ushort
from ctypes import windll, cdll
from ctypes import memset, addressof, sizeof, byref
from comtypes import GUID
from ceserial import Serial

import wintypex as w

# in wintypex
# ULONGLONG = c_ulonglong
# bt_addr = ULONGLONG
# BT_ADDR = POINTER(bt_addr)
# BT_ADDR_PTR = POINTER(BT_ADDR)

# uiportflags 
RFCOMM_PORT_FLAGS_REMOTE_DCB = 0x00000001 
RFCOMM_PORT_FLAGS_KEEP_DCD = 0x00000002 
RFCOMM_PORT_FLAGS_AUTHENTICATE = 0x00000004 
RFCOMM_PORT_FLAGS_ENCRYPT = 0x00000008 

core = windll.coredll # windll.kernel32

RegisterDevice = core.RegisterDevice # HANDLE RegisterDevice(   LPCWSTR lpszType,   DWORD dwIndex, LPCWSTR lpszLib,   DWORD dwInfo );
RegisterDevice.restype = w.HANDLE
RegisterDevice.argtypes = [ w.LPCWSTR, w.DWORD, w.LPCWSTR, w.DWORD ]
DeregisterDevice = core.DeregisterDevice

GetLastError = core.GetLastError
SetLastError = core.SetLastError

# For BT_COM support.
class PORTEMUPortParams(Structure):
    _fields_=[
        ( 'channel', w.INT),
        ( 'flocal', w.INT ),
        ( 'device', w.BT_ADDR),
        ( 'imtu', w.INT ),
        ( 'iminmtu', w.INT ),
        ( 'imaxmtu', w.INT ),
        ( 'isendquota', w.INT ),
        ( 'irecvquota', w.INT ),
        ( 'uuidService', GUID ),
        ( 'uiportflags', w.UINT)
    ]
    def __init__( self, device_str=None, 
                    flocal=False, 
                    channel = None,
                    uuidService=None, 
                    uiportflags=None ):
        if device_str is None and not flocal:
            raise Exception( 'device address missing in client mode.' ) 
        memset( addressof(self), 0, sizeof(self) ) # memset (&pp, 0, sizeof(pp));
        if not flocal:
            bta = c_ulonglong( int(device_str, 16) )
            print(bta)
            bta_p = w.BT_ADDR( bta )
            self.deivce = bta_p
        self.flocal = w.INT( flocal )
        # https://stackoverflow.com/questions/27302060/how-to-check-if-an-paired-bluetooth-device-is-a-printer-or-a-scanner-android
        # " Note: most common UUID (scanners, printers, Mice) 
        # have the generic UUID 0001101-0000-1000-8000-00805F9B34FB "
        if uuidService:
            self.uuidService = uuidService
        else:
            self.uuidService = GUID("{00001101-0000-1000-8000-00805F9B34FB}")
        if uiportflags:
            self.uiportflags = uiportflags
        if channel:
            self.channel = channel & 0xff   # pp.channel = channel & 0xff;

print('class defined.')
print( "try uuidService" )
pp = PORTEMUPortParams('dc1d30428b19')      # PORTEMUPortParams pp;
# pp.uiportflags = RFCOMM_PORT_FLAGS_AUTHENTICATE
# pp.uiportflags = RFCOMM_PORT_FLAGS_REMOTE_DCB
pp.uiportflags = RFCOMM_PORT_FLAGS_REMOTE_DCB | RFCOMM_PORT_FLAGS_AUTHENTICATE

#HANDLE h = RegisterDevice ("COM", index, "btd.dll", (DWORD)&pp );
for i in range (1,10):
    index = i
    SetLastError( w.DWORD(0) )
    h = RegisterDevice(u"COM", index, u"btd.dll", w.DWORD( addressof(pp) ) )
    if h :
        try:
            print( 'handle=', h )
            print( "COM%s" % index )
            s = Serial( port="COM%s:" % index, open_existing=True )
            s.open()
            s.write(u'HELLO\r\n')
            s.flushOutput()
    #                s.write(u'HI\r\n')
    #                s.flushOutput()
            s.close()
        except:
            pass
    #            sleep(2)
        DeregisterDevice( h )
        break
    else:
        print('failed', GetLastError())
    sleep(1)

On Windows Mobile, two methods to create a port exist in the library, the first is class BluetoothSerialPort, this creates a connection immediately _but the underlying API it uses is rather unreliable, and it seems not to work at all on various device types._ The second is BluetoothDeviceInfo.SetServiceState as for Win32, this manually configures the necessary Registry settings and is reliable but might require a reboot before the port becomes available, and again the name of the new port is not returned.

https://github.com/inthehand/32feet/wiki/Bluetooth-Serial-Ports

a total waste of time...

PS: To control the bluetooth printer, wrapping the winsock functions in ctypes and communicating with the printer via bluetooth socket works flawlessly after some trial and error.