What's wrong with FND_WEB.PING in Release 12?

As we know , in 11.5.8, we can use http://<host>:<port>/pls/VIS/mypkg to call enabled plsql package. To testing availability of pl/sql web agent, Oracle has a testing package fnd_web.ping. But in R12,fnd_web.ping returns http 404 error page. Don't know why. Maybe it's because of the listener.