Dev Containers: Possible bug with "appPort" property

[ma-Tehwush]

In devcontainers.json when I have: "appPort": ["8000:8000"] and I build container, ports are like this:

But when I have "appPort": [8000] they are like this:

I thought these two settings were doing the same. But actually, bare 8000 number forwards only 127.0.0.1 which won't allow connections from outside of the host machine.

Is it a bug or a feature?

[chrmarti]

The hover on the "appPort" property shows:

Application ports that are exposed by the container. This can be a single port or an array of ports. Each port can be a number or a string. A number is mapped to the same port on the host. A string is passed to Docker unchanged and can be used to map ports differently, e.g. "8000:8010".

This could be clarified a bit by saying that the number syntax will only listen on that port on the loopback network interface.

[ma-Tehwush]

Thank you for clarification :)

Actually I only have read docs from:

• https://code.visualstudio.com/docs/devcontainers/containers#_publishing-a-port
• https://containers.dev/implementors/json_reference/#image-specific

I would say these also could be improved.