Best way to disconnect socket when applicationDidEnterBackground: ?

[csar4231]

I'm trying to close the socket when application enter in background and make a [socketIO disconnect] , I have seen that the event is send but nothing is received because app is in background.
When you enter in foreground again sometimes your receive the disconnect message, other times you don't receive nothing.
Wich is the correct way to close the socket when entering in background?
Thanks in advance.