There are multiple ways to publish a port of an application. Basically, you can use EXPOSE during the docker build process and then, on using docker run use the parameter -P to publish all exposed ports of said Image to the external IP of the node. You are also free to expose said ports manually via -p, i.e. -p="8080:80" to expose the port 80 of the container to the port 8080 of the host. Without giving an external port, like -p="80" you'll export the port 80 of the container to an random port. You can also lock the port export to a specified interface of the host, i.e. with -p="192.168.2.6:8080:80". It is also possible to randomize the external port in that scenario: -p="192.168.2.6::80".
Docker Documentation on EXPOSE
Publish port in swarm mode
Publish service ports externally to the swarm