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Exposing only one port

General Discussions
#1

I have a web application that runs on localhost:8080. I have put it in a Docker container, and want the port 8080 exposed on the host machine. The only way I can seem to get this port on the hosts localhost is with:

$ sudo docker run --network=host container_name

This of course displays the html page, however the applicaation also runs a redis server on port 6379. When I start docker this port is available on the host, however the application cannot access it from within docker.

How do I make only the port 8080 exposed to the host machine, and other ports available for the application.

#2

This is what makes Docker share every port with its host. Remove that, and instead explicitly publish one or more ports, like --publish 8080:8080 or -p 8080:8080. (This also allows you to change the port mapping, like -p 1234:8080 to map port 1234 on the host to port 8080 in the container.)

See Container networking | Docker Documentation.

#3

To add to @avbentem you can also include the flag –expose which is a runtime flag that lets you expose a specific port or a range of ports inside the container.
In your case that would be

--expose 8080
#4

@ibosk, does --expose limit what is exposed by --network=host? (It does not expose ports to the host.)

#5

If you specify --net=host both the --expose and --publish flags will not take effect, or rather will be ignored.
In addition, if you provide just the --expose flag that only opens the port on the container, but it will not be mapped unless you also specify the -p flag, however you can use -p standalone if the port/ports are already exposed in the Dockerfile.