networking//Localhost

- `127.0.0.1` is the loopback address. Traffic never leaves the machine.

127.0.0.1 is the loopback address. Traffic never leaves the machine.

NOT part of the private IP ranges (not 10.x.x.x or 192.168.x.x), its own special class.

localhost:3000 on your machine is invisible to other LAN devices.

Inside a Docker container, localhost refers to the container itself, not the host.

Each container has its own loopback. ping localhost inside a container hits the container.