Docker - I'm attempting to run the hello-world example from the Docker site, but localhost:4000 renders nothing

Question

I'm referring to the example located here: https://docs.docker.com/get-started/part2/#build-the-app

My attempt to run the app works as expected:

docker_test docker run -p 4000:80 friendlyhello * Running on http://0.0.0.0:80/ (Press CTRL+C to quit)

But, when I navigate to localhost:4000, the page doesn't load. Instead, I see a message in Chrome that reads "This site cannot be reached."

Do you have any idea what I might be doing wrong?