Docker netstat

we can't list container's ESTABLISHED connections on the host OS.
to do that, we need:
  1. get image pid 
        docker inspect {container_id} | grep Pid
    or 
        docker inspect -f '{{.State.Pid}}' {container_id}
  2. exec commands 
         nsenter -t {pid} -n netstat | grep ESTABLISHED
     nsenter -t {pid} -n netstat -tpn | grep 3306
     nsenter -t {pid} -n ip addr