Android Client SDK close on session

version: Java SE Client v7.2.2, Android Client SDK v4.2.6

The interval between disconnect and reconnection is short. An existing session fails to close and a new session is initiated for connection.
How does the Android client ensure that the session is completely closed before each new connection?

Do you mean that you have evidence on the client side that the session is not closed?
Or do you want to make sure that the previous session is closed on the server side before opening a new one from the client?
Or do you mean anything else by a session that "fails to close"?