Selfhosted Linkage

You made a Minecraft server, but your friends can't join and port-forwarding won't work? This fixes that. Your friends install one mod, tick one box, and connect with a share code — no VPN app, no account, no router settings.

Open source. Self-hostable. Nothing phones home to us.

Why your friends can't join

You probably did everything right — the server runs, LAN friends can join — but friends over the internet can't, and the "port forwarding" step just doesn't work. This is almost never your fault. Most home ISPs no longer give you your own public IPv4; they put you behind CGNAT, where many homes share one address inside the ISP's equipment that you can't touch. Forward a port all you like — there's nothing on the other side to reach it.

(Quick check: if your router's WAN IP starts with 100.64.–100.127., that's CGNAT.)

How it works

Selfhosted Linkage connects the two computers peer-to-peer using iroh:

• Direct connection (what you want). The two machines hole-punch straight through their routers — as fast as your connections allow. This works most of the time.
• Relay fallback (when direct is impossible). Strict school/office firewalls or unlucky router pairs block hole punching; traffic then bounces through a relay. The public default uses shared free relays (fine for most; can be laggy under load).

You share a short connection code; your friend pastes it and joins. No accounts, no logins, nothing stored on our side.

Two modes

• Public mode (default). Zero setup — install, share the code, play. Uses iroh's public relays only as a last resort; most connections go direct.
• Self-hosted mode (optional, advanced). If one friend is consistently relayed and laggy, run your own relay on a cheap VPS near them and point the mod at it. You own the infrastructure — we never see your traffic. Guide →

Install

1. Install Fabric or NeoForge for Minecraft 1.21.1, plus this mod (client-side; every player installs it).
2. In-game, open the Selfhosted Linkage screen, tick the box, and enter your friend's connection code.
3. That's it — no port forwarding, no VPN app, no account.

Full walkthrough, downloads, and the "why can't my friends join?" explainer: https://linkage.blopybox.net

Open source & what's bundled

MIT licensed — source and a reproducible build script are public: https://github.com/Toswapxedzur/selfhosted-linkage

For full transparency: the jar bundles linkage-iroh, a small open-source Rust helper that does the P2P tunnelling (built from the iroh libraries). Its source and the exact build steps are in the repository, and it only connects to establish your peer-to-peer link — no telemetry, no data sent to the mod authors.

• Requires: Minecraft 1.21.1 · Fabric or NeoForge · Java 21 · client-side, every player
• No other mod dependencies.
• Issues / questions: https://github.com/Toswapxedzur/selfhosted-linkage/issues