The OnDisconnect event handler is invoked immediately before
the client is disconnected from the server. To implement
an event handler, the application should create a class derived from
the CHttpServer class, and then override this method.
This is an advisory event and it is not required for the
application to explicitly disconnect the client or perform any action.
The event handler cannot prevent the client from disconnecting.
Applications that implement a handler for this event should only use
it to update any private data that was associated with the client
session.