How to Build a Multiplayer Lobby in Unity with Socket.IO

Building a multiplayer lobby is where most Unity real-time projects fall apart. Not the networking part — that's the easy bit. The hard part is everything around it: players joining and leaving mid-session, the host disconnecting and taking the room with them, a player's phone screen locking for 30 seconds and losing their slot forever. Most tutorials stop at "connected". This one doesn't. This is a complete walkthrough of building a production-ready lobby in Unity using socketio-unity — room creation, join by code, ready states, host migration, and reconnect with a grace window. Every line of code is taken from the real Samples~/Lobby/ sample in the repo, so you can run it locally and pull it apart. Prerequisites Unity 2020.1+ Node.js (for the test server) socketio-unity installed via Window → Package Manager → Add package from git URL : https://github.com/Magithar/socketio-unity.git Architecture Overview Before writing a line of code, the architecture matters. A lobby has three disti