Multiplayer

Multiplayer Game Development

Networking architecture and synchronization principles.

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1. Architecture Selection

Decision Tree

What type of multiplayer?
│
├── Competitive / Real-time
│   └── Dedicated Server (authoritative)
│
├── Cooperative / Casual
│   └── Host-based (one player is server)
│
├── Turn-based
│   └── Client-server (simple)
│
└── Massive (MMO)
    └── Distributed servers

Comparison

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

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2. Synchronization Principles

State vs Input

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

Lag Compensation

Technique	Purpose
Prediction	Client predicts server
Interpolation	Smooth remote players
Reconciliation	Fix mispredictions
Lag compensation	Rewind for hit detection

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3. Network Optimization

Bandwidth Reduction

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

Update Rates

Type	Rate
Position	20-60 Hz
Health	On change
Inventory	On change
Chat	On send

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4. Security Principles

Server Authority

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

Anti-Cheat

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

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5. Matchmaking

Considerations

Factor	Impact
Skill	Fair matches
Latency	Playable connection
Wait time	Player patience
Party size	Group play

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6. Anti-Patterns

❌ Don't	✅ Do
Trust the client	Server is authority
Send everything	Send only necessary
Ignore latency	Design for 100-200ms
Sync exact positions	Interpolate/predict

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Remember: Never trust the client. The server is the source of truth.