Nevermind, I had to move my test file under thepackagename/TheClassName.class and then it runs fine.
However my real program [1] consisting of few jar-files still does not run on CentOS (while running fine on Windows).
I have to investigate more and will ask a separate question.
Regards Alex
[1]: https://github.com/afarber/jetty-newbie/tree/master/WebsocketHandler