claude-dev-suite Unity Netcode for GameObjects
Architecture
┌────────────┐ ┌───────────┐
│ Client │ RPCs │ Server │ authoritative
│ │◀───────▶│ (or Host) │ state — broadcasts via
│ predicts │ Vars │ │ NetworkVariable + RPC
└────────────┘ └───────────┘
Use server-authoritative: never trust the client for damage, currency, or movement validation.
NetworkBehaviour basics
public class PlayerController : NetworkBehaviour {
public NetworkVariable<int> Health = new(100,
NetworkVariableReadPermission.Everyone,
NetworkVariableWritePermission.Server);
[Rpc(SendTo.Server)]
public void FireRpc(Vector3 origin, Vector3 dir) {
if (!IsServer) return;
// server-side validation + spawn projectile
SpawnProjectileServerSide(origin, dir, OwnerClientId);
}
[Rpc(SendTo.NotMe)]
public void OnHitEffectRpc(Vector3 pos) {
// VFX on every client except sender
}
}
RPC targets (Unity 6 attribute syntax)
SendTo |
Use |
|---|---|
Server |
Client → server requests |
Owner |
Server → owning client only |
NotOwner |
Server → all except owner (for own client prediction) |
Everyone |
Server → all clients (state broadcast) |
NotMe |
Common for VFX/SFX echo |
ClientsAndHost |
Mostly for host-aware logic |
Client-side prediction
- Client samples input → applies move locally + sends to server.
- Server validates → broadcasts authoritative state.
- Client reconciles: if server state diverges from prediction, replay inputs from divergence frame.
NGO doesn't ship a prediction system out-of-the-box — you build one with NetworkTransform.AuthoritativeMode = Owner + custom interpolation, or move to NetCode for Entities for first-class prediction.
Lag compensation (hit-scan)
When server processes a fire RPC:
- Read client RTT → rewind world state to
now - rtt/2. - Raycast against rewound colliders.
- Apply damage as if the shot landed at that historical state.
Implement via a ring buffer of past Transform/Collider snapshots (e.g. 1s @ 20Hz).
Unity Gaming Services integration
- Relay — NAT punchthrough; host gets a Join Code that clients use.
- Lobby — pre-game rooms with metadata; passes Relay Join Code to clients.
- Matchmaker — skill/region-based queue; spins up Multiplay servers.
- Multiplay — dedicated server hosting; build Linux server build, deploy via UGS dashboard.
Anti-patterns
| Anti-pattern | Fix |
|---|---|
| Client-authoritative damage | Always validate on server |
NetworkVariable<T> for every transform field |
Use NetworkTransform or batched update RPC |
| RPCs for high-frequency state | Use NetworkVariable (delta-compressed) or unreliable channel for visuals |
Singleton NetworkManager accessed before spawn |
Subscribe NetworkManager.OnServerStarted/OnClientConnectedCallback |
Mixing host-only logic with IsServer |
Use IsHost for host-specific code paths |
| Not pooling spawned NetworkObjects | NGO supports prespawned pools — use them |
Production checklist
- All damage / economy / inventory mutations server-side only
- Lag compensation for hit-scan weapons
- NetworkObject pools for projectiles / spawned entities
- Relay + Lobby tested on real network (cellular, restrictive NAT)
- Server build CI pipeline (Linux IL2CPP) → Multiplay deploy
- Client/server version negotiation on connect — reject mismatches
- Anti-cheat: server validates inputs, throttles RPC rate