Troubleshooting Exceptions: System.Net.HttpListenerException
An HttpListenerException is thrown when an error occurs processing a Hypertext Transfer Protocol request.
If the URI prefix is already registered, this exception will occur.
This exception is thrown by the HttpListener class and its associated classes when an error occurs during the initialization of the HttpListener or while creating or sending a response to an HTTP request.
This exception will be thrown if another HttpListener has already added the prefix uriPrefix.