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.

When to Use

This skill is applicable to execute the workflow or actions described in the overview.