After leaving the phone idle for too long (> 5 mins maybe), the user might already log out but won't know it

[monos63]

Binary version: first version on app store
Phone: iphone 4S

When I hit the home button and left the app, I put the phone idle for more than 5 mins.
After that I relaunched the app, it went to the last page I saw, and when I typed message in that there had no response (either on the server or on the target client). It looks like the user already timed out but it won't show nor update.

[monos63]

I tried again without hitting the home button (I simply clicked the power button and turned the screen off), and waited for 5 minutes. Then the same failure happened. I'm not sure if that was a background or foreground processes in this way though.