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 forwardin

Answer 1

The accepted answer is partially correct however since you can only link directories, which means you need to link the directory of the socket instead of the socket itself.

The following did it for me when I wanted to connect a postgres socket.

docker run -p 5432:5432 -v /run/postgresql:/run/postgresql -d --name postgres postgres

What this does is link the postgres socket file to your host system.

Answer 2

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