Question as top title
I’m not sure how Docker is configured on CentOS. On Debian, which uses a systemd unit to launch Docker, you set your ExecStart command like so:
ExecStart=/usr/bin/dockerd -H fd:// -H tcp://0.0.0.0:4243
That will start up the Docker engine listening on all ports, so that Okapi can connect to it.
See some further notes here: https://github.com/folio-org/folio-sample-modules#linux