## Instructions - Use Netcode for GameObjects v1.8+ on Unity 2022.3 LTS or newer for all new multiplayer work. - Always place exactly one NetworkManager + UnityTransport + NetworkSceneManager in a bootstrapped DontDestroyOnLoad scene. - Make player prefabs with NetworkObject + ClientNetworkTransform; never use legacy NetworkTransform without reason. - Default to ServerAuthoritative movement; use ownership only for cosmetic / input intent, validate on server. - Use ServerRpc for client->server input, ClientRpc for server->broadcast, and NetworkVariable with read/write perms for state. - Require ownership for ServerRpcs that move a player: `[ServerRpc(RequireOwnership=true)]`; set false only for global interactions. - Integrate Unity Gaming Services Lobby + Relay for NAT traversal; never expose direct IP in production builds. - Test with ParrelSync clones (2-3 clients + host) before any commit; cover host-migration failure message. - Handle OnClientDisconnectCallback and scene-event cleanup to avoid ghost NetworkObjects on rejoin. - Profile with Network Profiler and keep tick rate 30-60 Hz; compress vec3 and use delta updates. - Version network prefabs via GlobalObjectIdHash; warn on prefab list mismatch between builds. - Secure builds with connection approval JSON + rate limits; kick on malformed RPC payload. ## Examples - Example 1: User asks "add sprint sync" -> add NetworkVariable IsSprinting, ServerRpc RequestSprint, ClientRpc animation trigger. - Example 2: User asks "lobby then start" -> create UGS Lobby (max 4), allocate Relay, join code to clients, LoadScene on all. - Example 3: User asks "test locally" -> clone project with ParrelSync, run Host in editor, Client in clone, check ownership log. ## Workflows - New project workflow: Install NGO + UGS packages -> configure NetworkManager prefab list -> add Transport -> write PlayerBehaviour -> ParrelSync test. - RPC workflow: Define intent (who calls, who executes) -> choose ServerRpc/ClientRpc -> add validation -> test with latency simulation 100/200ms. - Lobby+Relay workflow: Authenticate anonymously -> Create Lobby -> Allocate Relay -> Update Lobby with join code -> Clients JoinLobby then JoinRelay -> NetworkManager.StartClient. - Debug workflow: Enable NGO logs -> reproduce desync -> inspect NetworkVariable deltas -> fix authority -> retest with 3 clones. ## Templates - Player NetworkBehaviour checklist: - [ ] NetworkObject checked, prefab in NetworkPrefabs list - [ ] ClientNetworkTransform added, authority set to Server - [ ] Input read in Update only if IsOwner - [ ] Movement applied in ServerRpc or NetworkVariable - [ ] OnNetworkSpawn registers, OnNetworkDespawn unregisters - ServerRpc template: ```csharp [ServerRpc(RequireOwnership = true)] void SubmitMoveServerRpc(Vector3 dir, ServerRpcParams rpc = default) { if (dir.sqrMagnitude > 1.1f) return; // validation transform.position += dir * speed * Time.deltaTime; } ``` - Connection approval snippet: ```csharp NetworkManager.Singleton.ConnectionApprovalCallback = (req, resp) => { resp.Approved = req.Payload.Length < 512; resp.CreatePlayerObject = true; }; ``` - ParrelSync test matrix: Host+1 client walk, Host+2 clients RPC spam, Host drop + rejoin. ## Tools - Packages: com.unity.netcode.gameobjects, com.unity.transport, com.unity.services.lobbies, com.unity.services.relay, ParrelSync (editor). - Editor: Network Profiler, Multiplayer Play Mode (Unity 6), Transport debug simulator. - Services: Unity Gaming Services dashboard for Lobby/Relay quotas and analytics. - External: Wireshark for packet check, Unity Cloud Build for synced client/host builds. ## Advanced - Use NetworkList and custom INetworkSerializable structs for inventories; avoid spamming ClientRpc per item. - Implement interest management via NetworkObject.CheckObjectVisibility for 16+ player scenes. - Add client prediction + reconciliation for fast shooters; fallback to server reconcile every 100ms. - Encrypt Relay join codes out-of-band; expire lobbies after 30s without heartbeat. - Handle scene switching with NetworkSceneManager.OnSceneEvent to respawn players deterministically. ## Documentation - Unity Netcode docs: https://docs-multiplayer.unity3d.com/netcode/current/about/ - UGS Lobby: https://docs.unity.com/ugs/en-us/manual/lobby-manual - Relay manual: https://docs.unity.com/ugs/en-us/manual/relay-manual - ParrelSync repo: https://github.com/VeriorPies/ParrelSync - Boss Room sample: https://github.com/Unity-Technologies/com.unity.multiplayer.samples.coop