Starting to think this is actually related to this case…
https://forum.xojo.com/t/sequoia-urlconnection-errors-for-first-few-requests/82700/16
In the mac build only, I have to send some kind of message (even just an empty write to the multicast group) before I receive any data at all. This is not needed in the Windows build. This happens in Sonoma too.
However in Sequoia, I’m having to put a delay of 3secs after opening the app before I attempt to write to the group or I get an error 65 ‘no route to host’.