The behaviour you’ve described in the failing case (specifically, in step 7) sounds right to me. I’m presuming that the TN3270 app is implementing the Telnet 3270 protocol. That’s based on TCP and, in general, TCP connections ‘tear’ when an app is suspended. I talk about this more in TN2277 Networking and Multitasking. Note that I’ve not updated that technote in a long time, so some things have drifted: Its terminology is somewhat out of date. Rather than talking about socket resource reclaim, I now say that the connection has been defuncted. Recent versions of iOS defunct on app suspend, so you don’t have to explicitly lock the device. As to why it’s working when your app isn’t installed, that’s hard to say. It’s possible that the TN3270 app is doing something weird to prevent defuncting, and the presence of your app is causing that to fail. Or it’s possible that there’s some sort of OS issue in play. It sounds like you’re able to reproduce this yourself. If so, I have an experiment for you
Topic:
App & System Services
SubTopic:
Networking