Came across a similar issue, one thing I don’t see mentioned here is you need to start docker to listen to both the network and a unix socket. All regular docker (command-line) commands on the host assume the socket.
sudo docker -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock -d &
will start docker listening to any ip address on your host, as well as the typical unix socket.