Related discussion: http://markmail.org/message/2yzhbttmen22gida
The typical use case is to run a server with a regular user which binds to a previledged port (i.e. 1~1024). To implement this kind of server, there needs to be a hook after ServerSocket.bind() and before ServerSocket.accept().
The first suggested solution was to provide a listener method to IoServiceListener, but it's not optimal because IoServiceListener is used for both acceptor and connector. Any better idea is appreciated.