BIDI_DEL_PORT(28h) is sent to the protocol converter and the port driver after a spooler port has been removed, even if the port driver is the application removing the port. It is not sent when a virtual port is removed. The protocol converter and port driver can free any instance data stored for the printer port.

Note: Port drivers are normally called to remove a port by the print object, but any application can remove a port by updating the system .INI file.