NLauncher Server Sync

Automatically sync your modpack to every player — no external hosting, no manual downloads.

NLauncher Server Sync is a server-side only mod that pairs with the NLauncher Minecraft launcher. Install it on your server and your players will automatically receive every mod and config update the moment they launch the game.

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How It Works

1. Server owner installs this mod on the server
2. Players add the server address in NLauncher ("Add Server Instance")
3. NLauncher connects to the mod's built-in sync API, previews the server info, and creates a matching instance
4. Every time a player launches, NLauncher checks for updates and syncs mods/configs automatically

No FTP. No Dropbox links. No "hey everyone, re-download the pack." Just update your server and players stay in sync.

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Features

Automatic Mod & Config Syncing

The mod scans your server's mods/ folder and configured config files, builds a manifest with SHA-256 hashes, and serves it to players via a lightweight built-in HTTP server. Players only download what's changed.

Minecraft Account Authorization

If the whitelist is on, only players who are whitelisted can sync.
If off, only players not banned on the server can sync.
Auth uses the player's Minecraft UUID — no extra accounts or tokens needed.

Client Mod Policies

Control what extra mods your players can use:

Policy	Behavior
Open	Players can add any client-side mods they want
Allowlist	Players can add mods that match your approved patterns (e.g., journeymap-*, sodium-*)
Strict	Only server mods allowed — extras get removed on sync

⚙️ Fully Configurable

All settings are in config/nlauncher-sync.toml:

• Server display name shown to players in the launcher
• Sync port (default 25580)
• Config file patterns — choose exactly which configs to push (supports globs)
• Excluded mods — skip server-only mods from syncing
• Client mod policy & allowlist

🔧 Server Commands

• /nlsync reload — Re-scan mods and configs and rebuild the manifest (e.g., after adding a new mod)
• /nlsync status — Show sync server status, mod count, config count, and policy

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Quick Start

For Server Owners

1. Drop the mod JAR into your server's mods/ folder
2. Start the server — a default config/nlauncher-sync.toml will be generated
3. Edit the config to set your server name, config sync patterns, and client mod policy
4. Open port 25580 (or your configured port) in your firewall / hosting panel
5. Tell your players to add your server in NLauncher — done!

For Players

1. Open NLauncher and go to Add Server Instance
2. Enter the server address (e.g., play.example.com)
3. Set the Join Port (default 25565) and Sync Port (default 25580) if your server uses non-standard ports
4. Click Connect — NLauncher will preview the server info (name, version, mod count)
5. Confirm to create the instance — mods and configs are downloaded automatically
6. Launch and play! Every future launch will sync any updates before starting the game

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Example Config

[server]
name = "My Awesome Server"
port = 25580

[sync]
configs = [
    "config/jei-common.toml",
    "config/create/*.toml",
    "config/sophisticatedbackpacks-common.toml"
]

exclude_mods = [
    "nlauncher_sync-*.jar"
]

[client_mods]
policy = "allowlist"
allowed = [
    "journeymap-*",
    "xaeros-minimap-*",
    "xaeros-worldmap-*",
    "optifine-*",
    "sodium-*",
    "iris-*"
]

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Requirements

• Minecraft 1.16.5+(Currently only 1.20.1 and 1.21.11 supported, but 1.16.5+ is planned)
• Mod Loader: NeoForge, Forge, Fabric, or Quilt
• NLauncher v0.5.0+ on the player's side
• Port 25580 (or configured port) must be accessible to players

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FAQ

Does this mod do anything on the client?
No. This is a server-side only mod. Players don't install it — they use NLauncher, which handles syncing automatically.

Do I need to host files somewhere?
No. The mod serves files directly from your server. No external hosting, CDN, or third-party services required.

What happens if the sync server is unreachable?
NLauncher will warn the player but still allow them to launch with whatever they last synced. No one gets locked out.

Can players still add client-side mods like minimaps or shaders?
Yes! Set your client mod policy to open or allowlist to let players add approved client-side mods alongside the server pack.

Does it sync resource packs or shader packs?
No. Minecraft already handles server resource packs natively, and shader packs are personal preference.

Is this secure?
The mod only serves files to players who are whitelisted or have joined your server before, verified by Minecraft UUID. Modpack files are not sensitive data, so UUID-based auth is appropriate for this use case.

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