How to use websockets for real-time gaming

Question

I want to make a 2 player pong game that uses websockets and node.js server. socket.io is used on both client and server. So far, my only experience is creating a chat application.

This is my first attempt at a multiplayer game so I'm not so familiar with network gaming. Should the server keep track of:

1. Every position the ball is at and how often or when?
2. player movement, player move left or right, what if I press and hold for awhile, how do I handle this? Should I send like a pressHoldStartPosition and pressHoldStopPosition? I guess this is easy if I only allow pressing but not holding down.

My thoughts:

1. When the ball hits a player, the client calculates velocity, start and end position and the other client should perform the correct animation from that.
2. No idea.

Answer 1

You are going to find books, upon books, about gaming networking.

In a brief description, here is what I find an interesting implementation: The server and the client calculate the physics of the game. The server will be a master, and have a correct state of all the entities, while the client will attempt to "predict" the state of the entities and keep a smooth animation. The client will get updated the correct state of entities from server periodically. In some games you might see entities suddenly teleport, and that is because client predicted position does not match the server actual position.

An entity state, such as the ball, or the players, usually contains information such as the position, velocity, button state (key down/key up).

Besides that, it is letting your imagination go wild and testing for the best solution and seeing what works. There are a lot to take into consideration, such as player latency and bandwidth.