Multiplayer

Multiplayer Game Development

> Networking architecture and synchronization principles.

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 |

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 |

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 |

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 |

5. Matchmaking

Considerations

| Factor | Impact |

|--------|--------|

| Skill | Fair matches |

| Latency | Playable connection |

| Wait time | Player patience |

| Party size | Group play |

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 |

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