nDPI is used by both ntop and nProbe for adding application-layer detection of protocols, regardless of the port being used. This means that
it is possible to both detect known protocols on non-standard ports (e.g. detect http non ports other than 80), and also the opposite (e.g. detect Skype traffic
on port 80). This is because nowadays the concept of port=application no longer holds.
See here for the list of supported protocols.