Container Networking

Part of the Docker course

You have run a web server in a container, watched it report that it is listening on port 80, and then opened http://localhost:80 in a browser and got nothing at all. The container is fine. The server is fine. Nothing is broken, and the reason is worth understanding properly rather than memorising a flag for.

A container gets its own network. Not a share of yours: its own, with its own IP address, its own set of ports, and its own view of what "localhost" means. Port 80 inside the container and port 80 on your machine are two different port 80s, in the same way that flat 3 in one building and flat 3 in another are two different flat 3s.