Bluetooth printer

Hi,
I connect a win Mobile 6 device in bluetooth connection with a printer. I implement a winsock scheme. In the following code on my mobile device (which is the client, the printer being the server) I need to reference the serviceClassID, but no idea where to take it from:

SOCKADDR_BTH Bnam;
...
Lnm = sizeof(SOCKADDR_BTH);
...
memset(&Bnam,0,Lnm);
Bnam.addressFamily = AF_BTH;
Bnam.btAddr = 0x37A68022C; // MAC address of the bluetooth printer
Bnam.serviceClassId = ???; // here is the problem !
if (connect(Pd->soc,(SOCKADDR *) // connect socket to printer
&Bnam,Lnm)==SOCKET_ERROR)
N = WSAGetLastError(); // 10014 error, whatever I put in serviceClassID
…….

What is supposed that I assign to that variable?
Thanks

PS: Looked into the registry key of the device corresponding to the printer (instatiated through the device discovery), I know the structure, but no member fits the serviceClassID