first get this: http://www.nirsoft.net/utils/cports.html find the program that is using the port 51990 and reconfigure it/close it/terminate it configure your shoutcast software to use port 51990 make sure your computer can be reached from the outside, you need public ip and not be behind a nat, your router must be configured to allow tcp port 51990 or your router must support/have upnp enabled go to http://www.canyouseeme.org/ and enter your ip and port 51990 and if it can see you that means everything is working on your side ip addresses starting with: 127.* 10.* 192.* 172.* are local ip addresses. those can't be accessed from the outside world to find out your public ip address go to: https://www.whatismyip.com/