I have concourse , sonarqube server running inside containers and when i am trying to connect to sonarqube server using concourse, it is showing me error i.e SonarQube server [http://localhost:9000] can not be reached
Not enough information to answer the question.
May be... If Concourse CI and SonarQube are in different containers, you have to specify http://container-name-with-sonar-qube:9000 in CI settings.