Currently the VISA Server is not available on the LabVIEW RT platform. It should be available in a future release of NI-VISA, however, I can not give any dates at this time. Although, VISA server is not available, you could write VI's for the RT system to execute the proper VISA communication and then return the information. For instance you could use VI Server to call VI's on the RT system that would do the communication and then return the data to the calling VI. Hope this was helpful.
Regards,
JR A.
Application Engineer
National Instruments