socket-multiplayer-loop

name	Socket Multiplayer Loop
description	Best practices for implementing client-server sync, fixed timestep loops, interpolation, and lag compensation.

Socket Multiplayer Loop Architecture

To build a real-time multiplayer snake game with Socket.io, adhere strictly to these principles:

1. Server-Authoritative State

• The backend Node.js server maintains the absolute source of truth (the position, mass, and state of all players and pellets).
• The Game Loop: Run a fixed-timestep game loop using setInterval (e.g., 20 ticks per second, 50ms delay).
• In every tick, process inputs, resolve collisions, update positions, and broadcast the state to all connected clients.

2. Spatial Partitioning for Performance

• With many pellets and body segments, naive O(N^2) collision checks will crash the server.
• Implement a Grid-based spatial hash or a QuadTree to quickly check local collisions (head vs. bodies, head vs. pellets).

3. Client Interpolation

• Because the server broadcasts at a low tick rate (20Hz) but the client renders at 60Hz, rendering raw server coordinates will look jagged and stuttery.
• Solution: The client holds a buffer of recent server snapshots. It renders the game state interpolating between the last two snapshots, adding a slight artificial delay (e.g., 100ms) to ensure smooth playback.

4. Input Prediction (Client-Side)

• When the local player moves or boosts, they should not wait for the server round-trip to see their snake turn.
• The client applies local inputs immediately to the camera and local snake visual representation.
• When the server snapshot arrives, the client corrects the local snake's position smoothly if it deviated from the server's truth.