Currently the "Bytes at port" property only applies to serial ports. If you are trying to write a generic driver or communications package that supports multiple connection types you cannot use the "bytes at port" since it will not work for anything but a serial connection. There is a related idea here which proposes the "Bytes at port" can be added to the event structure. It also suggests that this be expanded to other connection types. My idea suggests that at a minimum the VISA property node can be expanded.
Mark Yedinak Certified LabVIEW Architect LabVIEW Champion
"Does anyone know where the love of God goes when the waves turn the minutes to hours?" Wreck of the Edmund Fitzgerald - Gordon Lightfoot