Server.exe Error

unhandled Exception: system.net.HttpListenerExpection: The process cannt access the fill because it is being used by another process
at system.net.HttpListener.addallprefixes()
at system.net.HttpListener.start()
at server.programe.main(string[] args) in c:\user\case\desktop\phoenixRealms-master\server\program.cs:line 23

Confused on what to do.......