GdevelopMMOTestv1/README.md

GDevelop MMO Test Project

A small multiplayer game experiment built with GDevelop, MQTT, and JSON Server.

The goal of this project is to learn how real-time multiplayer game systems work by building a simple top-down multiplayer environment from scratch.

This is not intended to be a production MMO. It is a learning project focused on networking concepts, client/server communication, player synchronization, and game architecture.

Project Goals

• Learn multiplayer game architecture
• Experiment with real-time player movement synchronization
• Build a lightweight backend using self-hosted tools
• Learn how game clients communicate with servers
• Explore Docker-based deployment
• Create a foundation that could support small LAN multiplayer games

Current Technology Stack

Game Client

GDevelop

Used for:

• Game logic
• Scenes/rooms
• Player movement
• Object spawning
• UI
• Networking events

Real-Time Communication

MQTT (Mosquitto)

Used for:

• Player join events
• Player movement events
• Player leave events
• Room-based communication

Players communicate through MQTT topics based on their current room.

Database/API

JSON Server

Used for:

• Player accounts
• Persistent player information
• Player location data
• Player status

Current player data includes:

• Username
• Password
• Player color
• Current room
• Last room
• X/Y position
• Online status

Current Multiplayer Design

Players are separated into rooms/scenes.

When a player enters a room:

1. The client updates its current room.
2. The client queries JSON Server for existing players in that room.
3. Existing players are spawned locally.
4. The player publishes a join message over MQTT.

Example join message:

{
  "type": "join",
  "player_id": 1,
  "x": 320,
  "y": 192,
  "color": "player_color"
}

Movement Synchronization

The current movement system uses MQTT messages to synchronize players.

Movement events include:

Move Start

Sent when a movement key is pressed.

Example:

{
  "type": "move_start",
  "player_id": 1,
  "angle": 0
}

Move Stop

Sent when the key is released.

Includes the player's final position:

{
  "type": "move_stop",
  "player_id": 1,
  "x": 450,
  "y": 200
}

This allows clients to predict movement locally while periodically correcting position.

Backend Services

A future goal is to package the backend into Docker containers.

Planned services:

• MQTT broker
• JSON Server
• Python utility service

The Python service may eventually handle:

• Server time
• Day/night cycle management
• Player timeout detection
• Offline status cleanup
• Server-side events

Project Structure

Planned structure:

GameProject/
│
├── gdevelop/
│   ├── Game project files
│   └── Assets
│
├── docker/
│   ├── MQTT configuration
│   ├── JSON Server configuration
│   └── Utility services
│
├── database/
│   └── db.json
│
└── README.md

Current Status

Working:

• Player registration
• Player login
• Room switching
• MQTT communication
• Player spawning
• Multiple players visible in the same room
• Basic player synchronization

In Progress:

• Improved movement synchronization
• Better player disconnect handling
• Server-controlled time system
• Additional game mechanics

Future Ideas

Possible future features:

• Real-time day/night cycle
• Calendar events
• NPCs
• Persistent world state
• Inventory system
• Chat system
• Small LAN multiplayer deployment

Disclaimer

This project is primarily a learning exercise.

The current architecture is designed for experimentation and small-scale multiplayer use. It is not intended to be a secure public-facing MMO backend.

Security, authentication, and server authority would need significant improvements before public deployment.