This means that the port that your Ragic service is being used by another process, and you should stop that process before you start Ragic. The port that is being used is usually port 80 or port 443. The other process can be another Ragic service that you did not stop, or another web application like Windows IIS or Apache web server. Sometimes even applications like Skype can occupy port 80.
On a Linux server, you can use the following commands to find out which processes are listing on certain ports:
sudo lsof -i -P -n | grep LISTEN
sudo netstat -tulpn | grep LISTEN
sudo lsof -i:80 ## see a specific port such as 80 ##
sudo nmap -sTU -O IP-address-Here
On a Windows server, you can use the following command to find out all the ports being used by your applications on the server:
netstat -a -b
On Windows server, a service called "Web Deployment Agent Service" (MsDepSvc), which is part of IIS, may be the cause of this. Disabling the service will resolve the issue. This agent ran even after IIS was stopped/disabled.