Reply status on bridge

Hi, 

Congratulation for your nice work, I enjoy your application !

This pull pull request concern only the bridge socket. As far as I understand it, if a person is not authenticated or allow to access to a eventbus address, the message is juste ignore and lost. The client doesn't even know that it request need an authentication. For my understanding, I think It would be interesting to send that information : 
 * access_denied : when the user is authenticated but not allow
 * auth_required : when the user is not authenticated
 * auth_error : when we are enable to get user authentication information

This a suggestion of implementation because I really don't know if the I reply is a good or the best way.

Best regards,
Maneau