The InPort.vi and OutPort.vi are the VIs you will want to use. I don't believe there is much information on our website about this application but I would check out the internet. I did a search on google.com and came up with some stuff including some books on the subject matter. Also, here is a link to another Developer's Exchange thread that deals with this question.
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RNAME=ViewQuestion&HOID=506500000008000000620B0000&ECategory=LabVIEW.LabVIEW+General
Matt Kisler
Applications Engineer
National Instruments