Testing a Robust Netcode with Godot

Summary

Testing a Robust Netcode with Godot 2024-10-23 The biggest challenge I faced in developing Little Brats! was the online multiplayer part: synchronizing computers with sometimes consequent latency while maintaining the “fast-paced action game” aspect was far from simple. I'll tell you all about it! Lag compensation, prediction/reconciliation, etc. I'm not going to do a detailed tutorial on these points, as there are tons of them already, but to give you an idea of the principle: when a client computer performs an action (in my case, for example, pressing the button to slap another kid), the server will receive this action, calculate what's going on, and send the result back to the client... The problem is that even with a slight latency between the two computers, say 10ms, you end up with 20ms between pressing a button and receiving the result. It may not sound like much, but if you put a 20ms delay between each press of your keyboard keys and the execution of the resulting action, you're going to lose your mind in no time. In principle, this is compensated for by several techniques: in my case, the client “validates” the action performed by default and applies it in its local scene. This is a prediction. When the server receives the action, it rewinds the game by the duration of the latency (so, for example, 10ms backwards), applies the action, and runs the game universe again for the equivalent of 10ms, all in the background, without this being visible on the server's game. Then it sends the final state to the client, which when it receives it will either validate its own state if its prediction was correct, or correct it if the server returned a different result (this is called “reconciliation”). I'm not going to lie to you: it's very VERY complicated to implement all this reliably and “invisibly”. In other words, the people playing the game have to be as unaware of it as possible, and there has to be no camera “jumps”, inconsistencies, weird stuff... In practice,...