MQTT disconnect when the screen is locked

[chenzhijie]

I have given the mqtt client a unique clientId, and the client connect to my sever successfully.After setting up the messageHandler, I can receive message from others..However, when I lock the screen, the client disconnect. And the messageHandler is invalid, so I can't received the offline message.. I have noticed that the MQTT Client have a property keepAlive, but it doesn't work for me..Any idea?

[stefannilsson]

I guess this could be because of a non-granted continued background execution.
https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html