[build] ERROR: Sonar server 'http://localhost:9000' can not be reached

When you allow the 9000 port to firewall on your desired operating System the following error "ERROR: Sonar server 'http://localhost:9000' can not be reached" will remove successfully.In ubuntu it is just like as by typing the following command in terminal "sudo ufw allow 9000/tcp" this error will removed from the Jenkins server by clicking on build now in jenkins.