Grails applications by default run on 8080 port.But sometimes other applications may use the same port ,to solve this problem you need to do some simple console work while starting your application.Let say you want to run your application on port 9090 insted of default one.
grails -Dserver = 9090 run-app
Making changes on default port is simple like that , but if you wanna make this change permanent you can create BuildConfig.groovy file under directory “/grails-app/conf”
"grails-app/conf/BuildConfig.groovy"
