Why and when use EXPOSE?

[CDNxL]

I really don’t understand the point of using EXPOSE.

If I want to talks between containers I use named networks with bridge, if I want to access from outside I use port publish/mapping.

Why “expose” ports?

Thanks.

[rsesha]

Please look at this old thread

What is the use of EXPOSE in Docker file

Hi, I note that --link becomes deprecated in the recent docker version. This makes me think what is the use of EXPOSE in the docker file. What if I have “EXPOSE 8080”, but run the image without publishing any port. In this case, is the effect of “EXPOSE 8080” nil? Thanks.

[rsesha]

• EXPOSE` is a way of documenting
• –publish(or-p` ) is a way of mapping a host port to a running container port

[terpz (Martin Terp)]

Also, if there is ports that have been defined in EXPOSE, you can use “docker run -P” and it will auto map the ports that is listed in the image