Docker port mapping

Docker Desktop provides several networking features to make it easier to use.

When you run a container with the -p argument, for example:

$ docker run -p 80:80 -d nginx

Docker Desktop makes whatever is running on port 80 in the container (in this case, nginx) available on port 80 of localhost. In this example, the host and container ports are the same. What if you need to specify a different host port? If, for example, you already have something running on port 80 of your host machine, you can connect the container to a different port:

$ docker run -p 8000:80 -d nginx

Now, connections to localhost:8000 are sent to port 80 in the container. The syntax for -p is HOST_PORT:CLIENT_PORT.