Grails Programmer : How to change the default port of a Grails 3 App
By default a Grails 3 app will start in the port 8080. It is easy however to configure a different port. Edit
grails-app/conf/application.yml and add the next snippet at the bottom of the file.
--- server: port: 8090
Next time you run the app, it will listen in the port 8090.
Feb 2016, 27.