I'm working on a multi Massive Game ONLINE and came across the following problem.

Below a picture of the game running ONLINE.



I believe that is not possible I send data packets using different (structs lists) in client and server, if I'm wrong, please correct me!
So I'm a great difficulty to developing a communication in order to maintain an updated LIST of the Online Players in clients.

Below is another picture showing how I am working with structs communication on client and server



When the player enters the game, the server sends to him an updated list with all players online in moment.

On Client This struct list contains only one variable to the entity (handle) of the players.
Because this way, I can set all entities for you, and apply individual actions for (players entitys);

My problem is send this struct list to customers. because I can only send the same list of communication that I already use to send the information:
(path, angle, messages etc ...).

someone could tell me some suggestion?
How can I keep this list updated on the clients?