SendMessage() from CAsyncSocket to CDialog.

This is in reference to following post:

http://groups.google.co.in/group/microsoft.public.vc.mfc/browse_thread/thread/26d525c01a51ca3/cbc7666feab318ed?lnk=gst&q=nexolite#cbc7666feab318ed

here I wanted to implement the SendMessage() to dialog class method as
suggested by joe.
here is what his post was:

*************
void ConnectionManager::OnAccept(int nErrorCode)
    {
     if(nErrorCode == 0)
       { /* got it! */
        ConSock * sock = new ConSock;
        if(Accept(*sock))
           { /* got connection */
            pwnd->SendMessage(UWM_CONNECTED, (WPARAM)sock);
           } /* got connection */
        else
            ... deal with error
      } /* got it */
   else
      ... deal with error
   }

Note that this does not require ANY knowledge of what the parent class is,
what its type
is, the header file from the parent class, or anything else.

****
But here he is using pwnd (which in my code was CDialog*),
 but then if you are using pwnd, then how does it not require any knowledge
of the parent class?
or what is the way to SendMessage to the CDialog window?