How to connect to a database that is in docker?

Question

Docker

create a service

docker service create --detach --name registry --publish 5441:5440 registry:2

I do next

docker-compose build
docker-compose push

docker stack deploy --compose-file docker-compose.yml mystack

In the docker-compose.yml file, I set the
port for the database

ports:
      - 5440:5440

the database is being built, but I can't connect to it from the outside

Answer 1

https://github.com/eko/docker-symfony
here is a good example for symfony