Struggling to get JS8Call working with my Flex 6500. Everything works fine with WSJT-X using localhost:60002, but when I try the same settings in JS8Call I get "Hamlib error: IO error while opening connection to rig".

I've tested CAT and PTT - both pass. Audio is coming through DAX fine, I can see signals on the waterfall, but no decoding at all. Time sync is good via BTK timesync.

FlexRadio 6xxx rig selected, Network Server set to localhost:60002, SmartSDR CAT configured with TCP port. What am I missing here?

Check that your SmartSDR CAT TCP port is actually 60002 - it must match exactly. Also verify you have CAT control enabled in the SmartSDR CAT setup, not just the port defined.

I had similar issues until I realized the port number must correspond to the TCP port number set up in SSDR CAT. Also make sure the VFO slice assignment matches between SmartSDR CAT and JS8Call settings.

You can search the internet for setups with your hardware for WSJTx, because the configuration in WSJTx is identical to JS8Call. Try configuring WSJT-X first to verify your CAT setup, then copy those exact settings to JS8Call.