Unable to connect to remote Docker daemon

I have two virtual machines running Ubuntu, each with Docker installed. I can easily ssh from one VM into the other, and I want to be able to connect to the other VM’s Docker daemon. I am running:

sudo docker -H=tcp://[IP address of other VM]:2376 images

and I receive:
Cannot connect to the Docker daemon. Is the docker daemon running on this host?

The Docker service is started on both VMs, and I have exported DOCKER_HOST to the IP address. Is there something else I must do in order to connect to it?

It’s always a good idea to check your firewall rules to ensure each VM host OS can reach the other host’s port 2376 (in this instance), and any other ports needed to run the application.