godot-multiplayer

Godot Multiplayer (4.x high-level)

Connect peers, call functions remotely with @rpc, assign authority, and replicate state with MultiplayerSpawner/MultiplayerSynchronizer. Targets Godot 4.7 (ENet). Treat all client input as untrusted; keep the server authoritative.

When to use

• Use when adding networked multiplayer: hosting/joining over ENet, calling RPCs, assigning per-node authority, or auto-spawning/syncing nodes across peers.

When not to use: local split-screen (no networking); raw TCP/UDP/WebSocket protocol work (low-level PacketPeer); HTTP requests. For save/persistence → save-systems.

Core workflow

1. Create a peer (ENetMultiplayerPeer), call create_server(port, max) or create_client(ip, port), and assign it to multiplayer.multiplayer_peer. The server's unique ID is always 1; clients get random positive IDs.
2. Handle connection signals on multiplayer: peer_connected(id), peer_disconnected(id), connected_to_server, connection_failed, server_disconnected.
3. Define RPCs with @rpc(...). Call them on a Callable via rpc() (all peers) or rpc_id(peer_id) (one peer). Inside, multiplayer.get_remote_sender_id() tells you who sent it.
4. Keep RPC signatures identical on every peer that runs the script — Godot checksums all @rpc methods in a script; mismatches break silently.
5. Assign authority per node with set_multiplayer_authority(id); gate input/RPCs by is_multiplayer_authority().
6. Replicate state with MultiplayerSpawner (auto-instances scenes on clients) and MultiplayerSynchronizer (auto-syncs selected properties).
7. Validate on the server. Don't trust client-reported positions/results.

Patterns

1. Host or join (ENet)

const PORT := 7000
const MAX_PLAYERS := 8

func host() -> void:
    var peer := ENetMultiplayerPeer.new()
    var err := peer.create_server(PORT, MAX_PLAYERS)
    if err != OK:
        push_error("Cannot host: %s" % err); return
    multiplayer.multiplayer_peer = peer
    multiplayer.peer_connected.connect(_on_peer_connected)

func join(ip := "127.0.0.1") -> void:
    var peer := ENetMultiplayerPeer.new()
    peer.create_client(ip, PORT)
    multiplayer.multiplayer_peer = peer
    multiplayer.connected_to_server.connect(func(): print("connected"))

func leave() -> void:
    multiplayer.multiplayer_peer = OfflineMultiplayerPeer.new()