@eskimo The "Network" Instruments on the devices seem to show the same thing. The network connection was established, but no data flowed from the iOS17 device, while iOS 16 was working fine. The webRTC servers we used showed the same thing - the UDP connection was established, and the server sent plenty of packets to the device but received 0 in return.

Could it be one of the new 'privacy' settings that is being over-enthusiastic about this?

Haven't tried Xcode 13.3 but otherwise -yes. Device wise, the code has been in production for several years, server some 6 million+ Video visits. on iOS version 14, 15, 16.

It's using BoringSSL/OpenSSL so that should eliminate the crypto question. The source code is cross platform C++ code which I have needed to dive deeply into since I made flying toaster screen savers for a living. Since so much is virtual & delegated, it's hard to see exactly where it connects to the iOS hardware.

This isn't universally true - some of our in-house apps are working just fine - but one isn't.