Modpack Checker

A lightweight Fabric mod for Minecraft servers to verify that clients are using the correct modpack version.

Features

• Lightweight Version Checking: Simple version-based verification instead of complex modlist comparison
• Easy Configuration: Simple TOML files for server and client configuration
• Automatic Disconnection: Players with incorrect versions are automatically disconnected with helpful messages
• Vanilla Reload Integration: Configuration reloads automatically when using vanilla's /reload command
• Development Mode: Use version "0.0.0" to always allow joining (useful for development)

Installation

Server Setup

1. Install the mod on your server
2. The configuration file will be automatically created at config/modpack-checker-server.toml
3. Edit the configuration file to set your desired settings
4. Use /reload to apply configuration changes

Client Setup

1. Include this mod in your modpack
2. The configuration file will be automatically created at config/modpack-checker-client.toml
3. Edit the configuration file to set the current modpack version
4. Distribute the modpack to your players

Configuration

Server Configuration (config/modpack-checker-server.toml)

# Modpack Checker Server Configuration

# Enable or disable modpack version checking
enable = true

# Expected modpack version that clients must have
expected_version = "1.0.0"

# Kick messages for different scenarios
[messages]
# Message shown when client doesn't have the mod installed
no_mod = "Please install the Modpack: <your-modpack-link>"

# Message shown when client has wrong version (use {version} as placeholder)
wrong_version = "Please install modpack version {version}: <your-modpack-link+version>"

# Message shown when there's a server configuration error
server_error = "Server configuration error. Please contact an administrator." 

Client Configuration (config/modpack-checker-client.toml)

# Modpack Checker Client Configuration

# Current modpack version - this should match the server's expected version
# Use "0.0.0" for development (always allows joining)
version = "1.0.0"

How It Works

1. When a player connects, the server sends a version check request
2. If the client has the mod installed, it reads its configuration file and sends the version back
3. The server compares the client's version with the expected version from its configuration
4. If versions don't match (and client doesn't have dev version "0.0.0"), the player is disconnected with a helpful message

Configuration Reload

The mod automatically reloads its configuration when you use the vanilla /reload command. This allows you to change settings without restarting the server.

Error Messages

• No Mod: "Please install the ModpackChecker mod: https://triibu.tech/minecraft"
• Wrong Version: "Please install modpack version X.X.X: https://triibu.tech/minecraft"
• Server Error: "Server configuration error. Please contact an administrator."

Configuration Options

Server Options

• enable - Enable or disable version checking (true/false)
• expected_version - The version that clients must have
• messages.no_mod - Message shown when client doesn't have the mod
• messages.wrong_version - Message shown when client has wrong version (use {version} placeholder)
• messages.server_error - Message shown for server configuration errors

Client Options

• version - The current modpack version (use "0.0.0" for development mode)

Development Mode

For development purposes, you can set the client version to "0.0.0". Clients with this version will always be allowed to join any server, regardless of the server's expected version. This is useful when developing modpacks or testing configurations.

Singleplayer

The mod automatically detects singleplayer environments and disables version checking to avoid interfering with local gameplay.

Technical Details

• Uses Fabric's login networking for lightweight version verification
• No complex modlist comparison or checksum calculations
• Minimal network overhead
• Compatible with Fabric API 0.96.0+ for Minecraft 1.21.1
• Configuration files are automatically created with sensible defaults
• Uses night-config:toml (Licensed under LGPL) for robust TOML configuration parsing
• Environment-aware: Only generates and loads appropriate config files for the current environment