One to many in local network

Now i succeeded to connect the video with local server with my target android app
My next step is:

in local server the manager need to see employees and employees can see manager But emplyees don’t need to see each other how to achieve that target?
I am working on android java app ,and developing with android studio from windows 10
I have read this Documentation talkes about subscribe/unsubscribe but i haven’t found any related code in my project ,i need an easy steps to achieve my goal.