Please help!

How can i NOTIFY another controller from a controller? e.g. I have a network controller that responsible for send/receive message from/to server/client. This controller will run continuously. Also, i have a battle controller that will handle battle event. When a player took Attack action in the battle, he need wait other player take action. And then the battle will start. That mean the network controller will receive battle start message from server when all player took action and then the message will NOTIFY the battle controller to do players action. How can i do? Thanks