I have an app that receives commands from a pc via sms
The app responds to the command via the web, with the classics:
web1.Url = “http: //x.y.z.w: 80 / answer = gigetto”
web1.Get
If the app is loaded but in the background compared to other apps, it no longer responds
How to keep the code contained in the app functional, even in the presence of other apps that are currently in the foreground?
App Inventor apps not really can run in the background
see also @SteveJG's suggestion here
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.