Every developer knows the feeling. You fire up a new terminal, run a build command, and wait. The familiar green log line appears: Server running at http://localhost:3000 . For years, that was the sound of creation—the default, the comfortable, the predictable.
: This URL might be used in a development or testing environment for a software application. The localhost and specific port number indicate that it's not a publicly accessible service but rather one running locally.
# macOS / Linux lsof -i -P -n | grep LISTEN
Let’s assume you want to replicate this environment. Whether you are an AI hobbyist or a web dev, here is how you get a "new" instance running on localhost:11501.