normally, you use windows' DeviceIOControl API to open an access to driver. You have to supply the "exported" name of the driver to this function. However, IIRC this can be applied only to windows versions with NT kernel or NT derived kernel (Win Nt4/2k/XP).
Further communication with the driver is accomplished with IO control codes. Search for Windows APIs that deals with IOCTLs.
Another possibility would be to use WINSOCK interfaces if the driver already provide a "network software interface". However, I'm not sure about this WINSOCK solution at this point.