For using the RedPitaya as Vector Network Analyzer you will need some extra part: a coupler like the Mini Circuits ZFDC-10-1-SMA, that will be used in the reverse way, and a VNA calibration kit with open, short and load connector. Should be also really useful a pair of 10db attenuator and a SMA tee.
The software is made by two part: server for the RedPitaya and a client. I’ve use the Windows precompiled version on OSX via WINE: worked at first try.
The result are pretty good and beyond my expectation! The client is really clean and easy to use and the RedPitaya is working really nice and fast.