multiplayer

name	multiplayer
description	Multiplayer game principles — networking architecture, synchronization, security, matchmaking

Multiplayer Game Principles

Tham khảo từ agent-skills-hub/game-development/multiplayer.

1. Architecture Selection

Real-time competitive → Dedicated Server (authoritative)
Cooperative / Casual → Host-based (one player is server)
Turn-based → Client-server (simple)
Massive (MMO) → Distributed servers

Architecture	Latency	Cost	Security
Dedicated	Low	High	Strong
P2P	Variable	Low	Weak
Host-based	Medium	Low	Medium

2. Synchronization

Approach	Sync What	Best For
State Sync	Game state	Simple, few objects
Input Sync	Player inputs	Action games
Hybrid	Both	Most games

Lag Compensation

• Prediction — Client predicts server
• Interpolation — Smooth remote players
• Reconciliation — Fix mispredictions

3. Network Optimization

Technique	Savings
Delta compression	Send only changes
Quantization	Reduce precision
Area of interest	Only nearby entities

Data	Rate
Position	20-60 Hz
Health	On change
Inventory	On change

4. Security — Server Authority

Client: "I hit the enemy"
Server: Validate:
  → did projectile actually hit?
  → was player in valid state?
  → was timing possible?

Cheat	Prevention
Speed hack	Server validates movement
Aimbot	Server validates sight line
Item dupe	Server owns inventory
Wall hack	Don't send hidden data

Anti-Rationalization

Excuse	Reality
"Trust client cho đơn giản"	Hack dễ dàng → game chết
"Gửi tất cả dữ liệu mỗi frame"	Bandwidth bùng nổ, lag
"P2P rẻ hơn, dùng P2P"	No authority = cheating everywhere

Red Flags

• Client-side authority
• Sync exact positions (không interpolation)
• Gửi full state mỗi frame

Verification

• Server is authority
• Lag compensation (prediction + interpolation)
• Delta compression + area of interest