Can docker port forward to a unix file socket on the host container?

Question

Running the following command fails:

sudo docker run -p unix:///tmp/file.sock:44444 -d image_name

Is something wrong with my port forwarding syntax or is a configuration like this not possible?

Answer 1

Docker's -p syntax won't take a unix socket:

-p=[]      : Publish a container᾿s port to the host (format:
             ip:hostPort:containerPort | ip::containerPort |
             hostPort:containerPort)

One solution would be to:

• Run your container without any -p specification, we'll name it "cont1" (--name cont1)
• Run a second container which:
  • Bind mounts the unix socket (-v /tmp/file.sock:/tmp/file.sock) to have it accessible from within the container
  • Links to the first container (--link cont1:cont1) to be able to connect to it
  • Runs a tool such as socat to route traffic from the unix socket to the "cont1:4444" endpoint

I'm not a socat expert, but the address specification you'll need should look like this: UNIX-LISTEN:/tmp/file.sock,fork,reuseaddr TCP4:cont1:4444