Exposing Services Running in a Docker Container Running in Virtualbox to Other Computers on a Local Network

Most of my experiments with Docker on my desktop machine to date have been focused on reducing installation pain and side-effects by running applications and services that I can access from a browser on the same desktop.

The services are exposed against the IP address of the virtual machine running docker, rather than localhost of the host machine, which also means that the containerised services can’t be accessed by other machines connected to the same local network.

So how do we get the docker container ports exposed on the host’s localhost network IP address?

If docker is running the containers via Virtualbox in the virtual machine named default, it seems all we need to do is tweak a couple of port forwarding rules in Virtualbox. So if I’m trying to get port 32769 on the docker IP address relayed to the same port on the host localhost, I can issue the following terminal command if the Docker Virtualbox is currently running:

VBoxManage controlvm "default" natpf1 "tcp-port32769,tcp,,32769,,32769"

which has syntax:

natpf<1-N> [<rulename>],tcp|udp,[<hostip>], <hostport>,[<guestip>],<guestport>

Alternatively, the rule can be created from the Network – Port Forwarding Virtualbox  settings for the default box:

To clear the rule, use:

VBoxManage controlvm "default" natpf1 delete "tcp-port32769"

or delete from the Virtualbox box settings Network – Port Forwarding rule dialogue.

If the box is not currently running, use:

VBoxManage modifyvm "default" --natpf1 "tcp-port32769,tcp,,32769,,32769"
VBoxManage modifyvm "default" --natpf1 delete "tcp-port32769"

The port should now be visible and localhost:32769 and by extension may be exposed to machines on the same network as the host machine by calling the IP address of the host machine with the value of the forwarded port on host.

On a Mac, you can find the local IP address of the machine from the Mac’s Network settings:

Simples:-)