Support forwarding ports from non-localhost hosts

[jarrodldavis]

The other Visual Studio Code Remote extensions support forwarding ports from non-localhost hosts inside the container, so GitHub Codespaces should support it too. This is useful for exposing ports from Docker Compose services, such as a database, without having to use the usual hack of putting both containers on the same network (like is done here and here).

I've tried doing this on Codespaces (even following these testing directions using this repository) and it doesn't work. forwardPorts entries in devcontainer.json appear to be ignored if they are a host:port string, and manually forwarding a port using a host:port string appears to silently drop the host and only forward the port from localhost in the container.

[shellerci]

If you checkout the devcontainer.json for forwardPorts they've got the disclaimer :

⚠️ Codespaces does not yet support the "host:port" variation of this property

Which I agree is less than optimal, although the "does not yet" wording gives me hope that this is on their todo list.

In the interim, I've been using using socat as a workaround.

Added this to my Dockerfile

RUN apt-get install socat

Added MySQL service to my docker-compose.yml

  cs-mysql:
    image: mysql:5.7
    restart: unless-stopped

Added this to my forwardPorts in devcontainer.json

forwardPorts: ["3306"]

And the following to my postCreate script

# socat TCP4-LISTEN:<PORT-TO-FORWARD>,reuseaddr,fork TCP:<SERVICE-NAME>:<PORT-TO-FORWARD> & 
socat TCP4-LISTEN:3306,reuseaddr,fork TCP:cs-mysql:3306 & 

[jarrodldavis]

Ah weird I must have missed that when reading the documentation before. I know it's still technically in beta but having Codespaces lag behind other Remote extensions like this is frustrating when trying to make a devcontainer.json setup that you want to work for both local Docker container usage and Codespaces. Hopefully the Codespaces team has time to work on closing this and other gaps soon. :)

And yeah, I also figured out that socat works as a workaround, but as you said it's less than ideal.

[longzheng]

In case anyone else was also looking for this, the disclaimer got moved to https://containers.dev/supporting#codespaces-specific-limitations