flask-uwsgi | Tutorial for setting up Flask with uWSGI Nginx | Learning library

-p 8080:8080 is equal to -p 0.0.0.0:8080:8080 where:

• 0.0.0.0 - address on the host to redirect from
• first 8080 - port to redirect from
• second 8080 - port of container (inside docker network)

So, your error message says that you cannot bind to port 8080 of the host (not your internal docker network).

This command allows you to access your container from host network (eg. from localhost:8080 to 8080 port of your container). Basically, it uses iptables to redirect packets from one network to another. So, when you call -p 8080:8080, it will redirect packets from port 8080 to your first container and when you call the same command for second container it fails, because port 8080 is already in use. You cannot you the single port to redirect to both containers at the same time.

Based on your description, you don't even need to publish ports to your flask-uwsgi containers, because you have a nginx proxy, which will allow you to access them based on host names. These ports will still be available inside your Docker network, you just won't publish then to your host OS.

If you still need to access your flask-uwsgi containers directly (without nginx), then you can publish them to different ports. Eg. first - -p 8081:8080, second - -p 8082:8080).