cCall   [pPortClose], hPort
or      eax, eax
jz      error_handler
 Called by the _VCOMM_CloseComm service to close a port. Uses the C calling convention.
If the PortOpen function calls the _VCOMM_Acquire_Port service, the PortClose function must call the _VCOMM_Release_Port service.
_PORTINFORMATION, PortOpen, _VCOMM_CloseComm