cmnd netstat -ano will show you the pid of any item blocking or using a port most often they dont just need to be forwarded but whatever has the port locked for its use(teamviewer skype and windows www services are some of these) and will have to be ended or redirected to another port .... u can find the program by its pid in the task manager
if you do not have the pid column available in processes then you can add it by clicking view select column and making sure the pid(process identifer) it checked