Update - The new 18.5 Beta 2 build from today 22F5053f completely resolves the issue.

I have tried many things, here and I am starting to suspect a bug in the beta. After getting EINTR once, I retry only to get EADDRINUSE over and over; before I give up. I have also tried setting the socket option SO_REUSEADDR and this does not help. I have also tried with and without O_NONBLOCK, no luck. While on mobile data, its always: connect()->EINTR->EADDRINUSE Switching to wifi (without restarting the app) and things start to work. This is happening from the "Packet Tunnel" network extension part of the app... something subtle has changed somwhere - Hopefully the beta developers are aware or have some insight.

Thanks Past Quinn™…and Present Quinn for the response (and countless others I have read over the years, while of lurking in the corner) We are handling EINTR, there is no crash and we do retry. Let me do some more research and maybe write a test driver and see if I can narrow this down. Our app has worked for years and started acting up on this seed.

Disabling "Multipath Networking" in Settings>Developer on the iPhone did the trick for me. Running iOS 17.1 (21B74) and XCode Version 15.0.1 (15A507)