/multiplayer-basics

name: multiplayer-basics
description: Use when implementing multiplayer — MultiplayerAPI, ENet/WebSocket peers, RPCs, and authority model

Multiplayer Basics in Godot 4.3+

All examples target Godot 4.3+ with no deprecated APIs. GDScript is shown first, C# follows.

**Related skills:** See **multiplayer-sync** for state synchronization and interpolation. See **dedicated-server** for headless export and server deployment.

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1. Multiplayer Architecture

Godot uses a **client-server model** built on top of `MultiplayerAPI`. One peer acts as the server; all others are clients. Every peer has a unique integer ID assigned by the network layer:

| Peer ID | Role | |---------|------| | `1` | The server (always) | | `2`+ | Connected clients — randomly generated unique IDs, **not** sequential |

**Multiplayer authority** is the concept of ownership over a node. Only the authoritative peer should read input and drive that node's state. By default the server (peer `1`) is the authority for every node. Call `set_multiplayer_authority(peer_id)` to transfer ownership to a client.

Server (peer 1)
    ├── Owns game state by default
    ├── Spawns and validates objects
    └── Routes RPCs
Client (peer 2, 3, …)
    ├── Sends input to server via RPC
    └── Receives state updates from server

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2. Setting Up ENetMultiplayerPeer

Both sides use the same three steps: create an `ENetMultiplayerPeer`, call `create_server(port, max_clients)` or `create_client(address, port)`, then assign it to `multiplayer.multiplayer_peer` and connect the four `MultiplayerAPI` signals. **Check the `create_*` return value** — it returns an `Error`, and a silent `ERR_CANT_CREATE` (port already in use) otherwise looks exactly like a hang.

The server is always peer ID `1`; clients receive randomly generated unique IDs, so never assume they are sequential.

Full server and client implementations with every signal handler, in GDScript and C#: [references/enet-setup.md](references/enet-setup.md)

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3. RPCs

`@rpc` (GDScript) / `[Rpc]` (C#) marks a method as callable across the network. Choose the mode and transfer settings carefully — they affect both security and performance.

RPC Modes

| Mode | Who may call it | Executes on | |------|-----------------|-------------| | `"authority"` (default) | Only the authority peer | The peer(s) it is sent to | | `"any_peer"` | Any connected peer | The peer(s) it is sent to |

Transfer Modes

| Mode | Delivery | Order | Use For | |------|----------|-------|---------| | `"reliable"` | Guaranteed | In-order | Chat, spawn events, important state | | `"unreliable"` | Best-effort | Unordered | High-frequency position updates | | `"unreliable_ordered"` | Best-effort | In-order per channel | Smooth movement streams |

GDScript

# chat.gd
extends Node

# Any peer can call; server validates then broadcasts to all peers.
@rpc("any_peer", "reliable")
func send_chat_message(text: String) -> void:
	if not multiplayer.is_server():
		return
	var sender_id := multiplayer.get_remote_sender_id()
	_broadcast_chat.rpc(sender_id, text)


# Only the authority (server) can call this; runs on every peer.
@rpc("authority", "reliable", "call_local")
func _broadcast_chat(sender_id: int, text: String) -> void:
	print("[%d]: %s" % [sender_id, text])


# Client → server: request to spawn an object.
@rpc("any_peer", "reliable")
func request_spawn(scene_path: String, spawn_position: Vector2) -> void:
	if not multiplayer.is_server():
		return
	# Server validates and performs the actual spawn.
	var scene: PackedScene = load(scene_path)
	if scene == null:
		return
	var instance := scene.instantiate()
	instance.global_position = spawn_position
	get_tree().root.add_child(instance)


# High-frequency sync; unreliable_ordered + a channel keeps this off other RPC traffic.
@rpc("authority", "unreliable_ordered", "call_local", 1)
func sync_position(pos: Vector2) -> void:
	global_position = pos

**Sending to specific peers:**

# Send to everyone (including self if call_local is set):
send_chat_message.rpc("Hello!")

# Send to one specific peer:
send_chat_message.rpc_id(target_peer_id, "Hello!")

C#

// Chat.cs
using Godot;

public partial class Chat : Node
{
    // Any peer can call; executes on the server only.
    [Rpc(MultiplayerApi.RpcMode.AnyPeer, TransferMode = MultiplayerPeer.TransferModeEnum.Reliable)]
    public void SendChatMessage(string text)
    {
        if (!Multiplayer.IsServer()) return;
        int senderId = Multiplayer.GetRemoteSenderId();
        Rpc(MethodName.BroadcastChat, senderId, text);
    }

    // Authority only; runs on every peer including the caller.
    [Rpc(MultiplayerApi.RpcMode.Authority,
         CallLocal = true,
         TransferMode = MultiplayerPeer.TransferModeEnum.Reliable)]
    private void BroadcastChat(int senderId, string text)
        => GD.Print($"[{senderId}]: {text}");

    // Client → server: request a spawn.
    [Rpc(MultiplayerApi.RpcMode.AnyPeer, TransferMode = MultiplayerPeer.TransferModeEnum.Reliable)]
    public void RequestSpawn(string scenePath, Vector2 spawnPosition)
    {
        if (!Multiplayer.IsServer()) return;
        var scene = GD.Load<PackedScene>(scenePath);
        if (scene == null) return;
        var instance = scene.Instantiate<Node2D>();
        instance.GlobalPosition = spawnPosition;
        GetTree().Root.AddChild(instance);
    }

    // High-frequency position sync.
    [Rpc(MultiplayerApi.RpcMode.Authority,
         CallLocal = true,
         TransferMode = MultiplayerPeer.TransferModeEnum.UnreliableOrdered,
         TransferChannel = 1)]
    public void SyncPosition(Vector2 pos)
        => GlobalPosition = pos;
}

**Sending to specific peers in C#:**

// Broadcast to all:
Rpc(MethodName.SendChatMessage, "Hello!");

// Send to one peer:
RpcId(targetPeerId, MethodName.SendChatMessage, "Hello!");

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4. Authority Model

Every node has exac