Is it possible to have a Docker container access ports opened by the host? Concretely I have MongoDB and RabbitMQ running on the host and I’d like to run a process in a Docker container to listen to the queue and (optionally) write to the database.
I know I can forward a port from the container to the host (via the -p option) and have a connection to the outside world (i.e. internet) from within the Docker container but I’d like to not expose the RabbitMQ and MongoDB ports from the host to the outside world.
EDIT: some clarification:
Starting Nmap 5.21 ( http://nmap.org ) at 2013-07-22 22:39 CEST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00027s latency).
PORT STATE SERVICE
6311/tcp open unknown
joelkuiper@vps20528 ~ % docker run -i -t base /bin/bash
root@f043b4b235a7:/# apt-get install nmap
root@f043b4b235a7:/# nmap 172.16.42.1 -p 6311 # IP found via docker inspect -> gateway
Starting Nmap 6.00 ( http://nmap.org ) at 2013-07-22 20:43 UTC
Nmap scan report for 172.16.42.1
Host is up (0.000060s latency).
PORT STATE SERVICE
6311/tcp filtered unknown
MAC Address: E2:69:9C:11:42:65 (Unknown)
Nmap done: 1 IP address (1 host up) scanned in 13.31 seconds
I had to do this trick to get any internet connection withing the container: My firewall is blocking network connections from the docker container to outside
EDIT: Eventually I went with creating a custom bridge using pipework and having the services listen on the bridge IP’s. I went with this approach instead of having MongoDB and RabbitMQ listen on the docker bridge because it gives more flexibility.
