Node.js printed this

Error: listen EADDRINUSE: address already in use :::3000

What it meansYour server tried to bind to port 3000, but another process is already listening on that port, so the operating system refused.

The first thing to checkAn earlier instance of the dev server is often still running; find it with lsof -i :3000 and kill it, or start your app on a different port.

The walrus saysSomething else is on port 3000. It is usually you, from yesterday.