First you'll have to make sure that the GPIB-ENET/100 is confiured properly. Refer to Chaptor 2 and 4 of this manual:
Afterwards run the Diagnostic Utility again.
For your C application, you must include the NI-488.2 header file in your source code. The Ni-488.2 is accessed through the 32-bit DLL, gpib-32.dll.
Several sample GPIB applications are included with ni-488.2. Use those as a guidefor your own application development.
More information about each NI-488 function can be found on the link below:
Dario Camargo
NI Brazil
#1162735