Author: James CE Johnson

ACE Tutorial 015
Building a protocol stream

The Handler object is our event handler. You can use either ACE_Event_Handler or ACE_Svc_Handler<> for the baseclass. I generally prefer the latter since it takes care of some housekeeping that I would otherwise be responsible for.

The class declaration is taken almost exactly from a previous tutorial. A good design will have a simple handler object that will collect data from the peer and pass it along to another object for processing. Again, keep it simple and delegate authority.

    // page08.html,v 1.12 1999/04/03 21:56:30 jcej Exp

    #ifndef HANDLER_H
    #define HANDLER_H

    #include "ace/Svc_Handler.h"

    #if !defined (ACE_LACKS_PRAGMA_ONCE)
    # pragma once
    #endif /* ACE_LACKS_PRAGMA_ONCE */

    #include "ace/SOCK_Stream.h"
    #include "Protocol_Stream.h"

    /* Just your basic event handler.  We use ACE_Svc_Handler<> as a
       baseclass so that it can maintain the peer() and other details for
       us.  We're not going to activate() this object, so we can get away
       with the NULL synch choice.  */
    class Handler : public ACE_Svc_Handler <ACE_SOCK_STREAM, ACE_NULL_SYNCH>
    {
    public:
      Handler (void);
      ~Handler (void);

      // Called by the acceptor when we're created in response to a client
      // connection.
      int open (void *);

      // Called when it's time for us to be deleted.  We take care of
      // removing ourselves from the reactor and shutting down the peer()
      // connectin.
      void destroy (void);

      // Called when it's time for us to go away.  There are subtle
      // differences between destroy() and close() so don't try to use
      // either for all cases.
      int close (u_long);

    protected:
      // Respond to peer() activity.
      int handle_input (ACE_HANDLE);

      // This will be called when handle_input() returns a failure code.
      // That's our signal that it's time to begin the shutdown process.
      int handle_close (ACE_HANDLE,
                        ACE_Reactor_Mask mask);
    private:

      // Like the Client, we have to abide by the protocol requirements.
      // We use a local Protocol_Stream object to take care of those
      // details.  For us, I/O then just becomes a matter of interacting
      // with the stream.
      Protocol_Stream stream_;

      Protocol_Stream &stream (void)
      {
        return this->stream_;
      }
    };

    #endif /* HANDLER_H */

[Tutorial Index] [Continue This Tutorial]