Create a Complete Online Co-Op Multiplayer Game in Godot 4

 Creating a Complete Online Co-Op Multiplayer Game in Godot 4 is a major but highly rewarding project. Godot 4 introduced significant improvements to its networking architecture, making it more capable of handling multiplayer games, including online co-op experiences.

In this guide, we’ll walk you through building a basic online co-op multiplayer game using Godot 4’s high-level multiplayer API. This game will allow multiple players to connect over a network and interact in a shared game world.

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🎮 Project Overview

Game Concept

A top-down 2D co-op game where players control characters that can move around, collect items, and interact with each other. All players will see each other's movements in real time.

Key Features:

• Host or join a multiplayer session

• Synchronize player movement across the network

• Use Godot’s high-level multiplayer API

• Optional: Chat system or shared inventory

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🧰 Tools & Technologies

• Godot 4.x

• GDScript

• Godot’s High-Level Multiplayer API

• Optional: ENet (UDP) for reliable communication

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📁 Project Structure

bash
/project/
│
├── scenes/
│   ├── MainMenu.tscn
│   ├── Game.tscn
│   ├── Player.tscn
│
├── scripts/
│   ├── main_menu.gd
│   ├── game.gd
│   ├── player.gd
│
├── assets/
│   └── (sprites, sounds, etc.)
│
└── project.godot

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🏗️ Step 1: Set Up the Project

1. Open Godot 4.

2. Create a new project named OnlineCoopGame.

3. Add a scenes/, scripts/, and assets/ folder.

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🎛️ Step 2: Create the Main Menu Scene

MainMenu.tscn allows the player to host or join a game.

Scene Structure:

less
MainMenu (Control)
├── VBoxContainer
│   ├── Button (text: "Host Game")
│   ├── Button (text: "Join Game")
│   ├── LineEdit (placeholder: "Enter IP")

Script: main_menu.gd

gdscript
extends Control

@onready var host_btn = $VBoxContainer/Button
@onready var join_btn = $VBoxContainer/Button2
@onready var ip_input = $VBoxContainer/LineEdit

func _ready():
    host_btn.pressed.connect(_on_host_pressed)
    join_btn.pressed.connect(_on_join_pressed)

func _on_host_pressed():
    var peer = ENetMultiplayerPeer.new()
    peer.create_server(12345)
    multiplayer.multiplayer_peer = peer
    get_tree().change_scene_to_file("res://scenes/Game.tscn")

func _on_join_pressed():
    var ip = ip_input.text
    var peer = ENetMultiplayerPeer.new()
    peer.create_client(ip, 12345)
    multiplayer.multiplayer_peer = peer
    get_tree().change_scene_to_file("res://scenes/Game.tscn")

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🌍 Step 3: Create the Game Scene

Game.tscn will hold the actual game world.

Scene Structure:

scss
Game (Node2D)
├── PlayerSpawner (Node2D)
├── Player (placeholder instance)

Remove the placeholder Player instance — we’ll spawn it in code.

Script: game.gd

gdscript
extends Node2D

@onready var player_spawner = $PlayerSpawner
var PlayerScene = preload("res://scenes/Player.tscn")

func _ready():
    multiplayer.peer_connected.connect(_on_peer_connected)
    multiplayer.peer_disconnected.connect(_on_peer_disconnected)

    if multiplayer.is_server():
        spawn_player(multiplayer.get_unique_id())
    else:
        rpc_id(1, "request_spawn", multiplayer.get_unique_id())

@rpc("any_peer")
func request_spawn(peer_id: int):
    if not multiplayer.is_server():
        return
    spawn_player(peer_id)

func spawn_player(peer_id: int):
    var player = PlayerScene.instantiate()
    player.name = str(peer_id)
    add_child(player)
    player.set_multiplayer_authority(peer_id)
    player.global_position = player_spawner.global_position

---

🧍 Step 4: Create the Player Scene

Player.tscn

Scene Structure:

scss
Player (CharacterBody2D)
├── Sprite2D
├── CollisionShape2D

Assign a simple shape and sprite to represent the player.

Script: player.gd

gdscript
extends CharacterBody2D

@export var speed: float = 200.0
@onready var sprite = $Sprite2D

func _ready():
    if not is_multiplayer_authority():
        set_process_input(false)

func _physics_process(delta):
    if is_multiplayer_authority():
        var input_vector = Vector2(
            Input.get_action_strength("ui_right") - Input.get_action_strength("ui_left"),
            Input.get_action_strength("ui_down") - Input.get_action_strength("ui_up")
        ).normalized()
        
        velocity = input_vector * speed
        move_and_slide()

        rpc_unreliable("sync_position", global_position)

@rpc("unreliable")
func sync_position(pos: Vector2):
    if not is_multiplayer_authority():
        global_position = pos

This code allows player movement only for the authority (the controlling client), and synchronizes position to others using rpc_unreliable().

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🧪 Step 5: Test the Multiplayer Game

1. Run the project.

2. Click "Host" on one instance.

3. Click "Join" on another instance using localhost as the IP.

4. You should see both players moving independently.

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💡 Optional Features to Expand

1. In-Game Chat

Add a TextEdit and LineEdit to the game scene and send messages via rpc().

gdscript
@rpc("any_peer")
func broadcast_message(message: String):
    $ChatBox.text += message + "\n"

2. Collectibles or Tasks

Create an item scene with a CollisionShape2D and detect overlaps.

Use rpc() to tell the server to destroy collected items and sync that to all clients.

3. UI for Player Count

Show how many players are connected using multiplayer.get_peers().

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🛠️ Troubleshooting Tips

• Always test locally with multiple instances using localhost.

• Use set_multiplayer_authority() for player nodes.

• Remember: Server handles spawning and object ownership.

• Use rpc() and rpc_id() for communication.

• Always verify is_multiplayer_authority() before allowing input or movement.

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🌐 Hosting Online

To allow players to connect over the internet:

• You must port forward port 12345 on your router.

• Share your public IP with your friend.

• Alternatively, use a relay server or a dedicated VPS.

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🚀 Final Thoughts

You now have a working online co-op multiplayer game in Godot 4!

This basic setup lays the foundation for much more complex games — from co-op dungeon crawlers to multiplayer farming sims. The powerful networking system in Godot 4 makes real-time multiplayer development much more accessible.

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✅ Summary

Feature	Implemented
Host/Join System	✅
Player Movement Sync	✅
Scene Management	✅
Multiplayer Authority	✅
RPC Communication	✅

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📁 Want the Complete Project?

Let me know, and I can generate a ready-to-use downloadable project or walk you through exporting it for PC/Web.