To write a file event handler plug-in you have to create a singleton class that derives from Node, and overrides the method Node::OnNodeEvent(). This class would typically have an attribute of type aptr<FileEvent> which acts as an event receiver. You would next connect the attribute to the Kernel::m_pFileEvent transmitter. For example:

// There will be one global instance of our class, which catches all the file events.  
FileEventHandler g_cHandler;  

// One time initialization. This is a static function.   
void FileEventHandler::Initializer( void )  {
    g_cHandler.m_pEvent.Connect( Kernel()->m_pFileEvent );
};

For more information see the file event handler example project.