TCP Client/Server Networking in Python -- 2

I need to use Python to implement server and client sockets. I created a server, client, client_handler (server uses it to thread clients), and menu class (on server-side). I have created a successful connection already between the server and the client and am able to pass info back and forth using pickle. I need help understanding concepts needed to create a simple protocol in which the server can communicate with the client and send over a menu with options. This menu provides options such as "send a message" where when this option is selected, the client sends a request containing the option selected, the message entered by the user, and the recipient id. Once the server receives these requests, it iterates over a list containing all the client's handler objects to match the recipent_id of the message. Finally, the server saves the message in the appropriate handler and acknowledges the client that the message was successfully saved.