IIRC iOS lets you connect to other apps on 127.0.0.1 just fine. But it won't work in the obvious use case of a foreground client and a background server without

IIRC iOS lets you connect to other apps on 127.0.0.1 just fine. But it won't work in the obvious use case of a foreground client and a background server without additional hacks, because the server can be suspended and the connection attempt alone won't wake it up.