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ryu_ldn_nx

Introduction

Introduction

Section titled “Introduction”

ryu_ldn_nx is a Nintendo Switch sysmodule that enables online local multiplayer (LDN) gaming by connecting to Ryujinx LDN servers over TCP — replacing ldn_mitm + lanplay + pcap with a single zero-config sysmodule. It ships as TitleID 4200000000000010 (boot2).

What is LDN?

Section titled “What is LDN?”

LDN (Local Wireless Communication) is Nintendo’s protocol for local multiplayer on the Switch. Games like Mario Kart 8 Deluxe, Super Smash Bros. Ultimate, and Monster Hunter Rise use LDN for “local play” features.

Normally, LDN requires players to be physically close to each other. ryu_ldn_nx intercepts LDN calls and routes them through an online server, allowing you to play “local” multiplayer games with friends anywhere in the world.

How it Works

Section titled “How it Works”
┌─────────────┐      ┌──────────────┐      ┌─────────────────┐
│   Game      │─────▶│ ryu_ldn_nx   │─────▶│  Ryujinx LDN    │
│ (MK8 etc.)  │◀─────│  sysmodule   │◀─────│    Server       │
└─────────────┘      └──────────────┘      └─────────────────┘
      │                     │
      │              ┌──────┴───────┐
      │              │ Tesla Overlay│
      │              │  (status UI) │
      │              └──────────────┘
      │
  ┌────▼──────────────────────────────────┐
  │  PIA (Protocol Independent Application)│
  │  Game-level mesh networking over LDN   │
  └───────────────────────────────────────┘
  1. Game calls LDN services — When a game tries to create or join a local network
  2. Sysmodule intercepts — ryu_ldn_nx captures these calls via Atmosphere MITM
  3. Routes to server — Requests are converted to RyuLdn protocol and sent to the server
  4. Server coordinates — The server matches players and relays game data
  5. Game plays normally — From the game’s perspective, it’s just local play
  6. PIA mesh forms — After the LDN session is established, games use PIA for peer-to-peer data exchange over UDP through the proxy socket layer

Features

Section titled “Features”
  • Transparent operation — Games work without modification
  • PIA mesh compatibility — Broadcast delivery ensures all PIA mesh discovery packets reach every listening socket
  • Tesla overlay — See connection status and configure settings
  • Auto-reconnect — Fast first retry (200ms) then exponential backoff with jitter
  • TCP keepalive — Detects dead connections automatically
  • Low latency — Optimized for real-time gameplay with direct P2P option

Compatibility

Section titled “Compatibility”

ryu_ldn_nx works with games that use Nintendo’s LDN service, including:

  • Mario Kart 8 Deluxe
  • Super Smash Bros. Ultimate
  • Monster Hunter Rise
  • Animal Crossing: New Horizons
  • And many more…

Next Steps

Section titled “Next Steps”