You don’t need to exclude anything form this link. You should fully understand/write the code regarding the concept of MEP Duplex/Callback.
What is MEP (Message Exchange Pattern) in WCF?
A whiteboard that’s shared between many people, one as a drawer and the others as guessers. The drawer can draw on the white board, while the guessers receive the drawings and try to guess it. The first one, the drawer, writes a word describes what he’s drawing, without the guessers knowing it, then he starts to draw and the guessers try to guess the drawing