Author: James CE Johnson
Description: A first step towards using ACE productively

ACE Tutorial 002
Creating a Better Server

Now lets take a look at the new Logging_Handler:

    // page03.html,v 1.9 1999/04/03 21:56:23 jcej Exp

    #ifndef LOGGING_HANDLER_H
    #define LOGGING_HANDLER_H

    #include "ace/INET_Addr.h"

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

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

    /* Since we used the template to create the acceptor, we don't know if
      there is a way to get to the reactor it uses.  We'll take the easy
      way out and grab the global pointer.  (There is a way to get back to
      the acceptor's reactor that we'll see later on.)  */
    extern ACE_Reactor *g_reactor;

    /* This time we're deriving from ACE_Svc_Handler instead of
      ACE_Event_Handler.  The big reason for this is because it already
      knows how to contain a SOCK_Stream and provides all of the method
      calls needed by the reactor.  The second template parameter is for
      some advanced stuff we'll do with later servers.  For now, just use
      it as is...  */
    class Logging_Handler : public ACE_Svc_Handler <ACE_SOCK_STREAM, ACE_NULL_SYNCH>
    {
    public:

      /* The Acceptor<> template will open() us when there is a new client
        connection.  */
      virtual int open (void *)
      {
        ACE_INET_Addr addr;

        /* Ask the peer() (held in our baseclass) to tell us the address
          of the cient which has connected.  There may be valid reasons
          for this to fail where we wouldn't want to drop the connection
          but I can't think of one. */
        if (this->peer ().get_remote_addr (addr) == -1)
          return -1;

        /* The Acceptor<> won't register us with it's reactor, so we have
          to do so ourselves.  This is where we have to grab that global
          pointer.  Notice that we again use the READ_MASK so that
          handle_input() will be called when the client does something.  */
        if (g_reactor->register_handler (this,
                                         ACE_Event_Handler::READ_MASK) == -1)
          ACE_ERROR_RETURN ((LM_ERROR,
                             "(%P|%t) can't register with reactor\n"),
                            -1);

        /* Here's another new treat.  We schedule a timer event.  This
          particular one will fire in two seconds and then every three
          seconds after that.  It doesn't serve any useful purpose in our
          application other than to show you how it is done.  */
        else if (g_reactor->schedule_timer (this,
                                            0,
                                            ACE_Time_Value (2),
                                            ACE_Time_Value (3)) == -1)
          ACE_ERROR_RETURN ((LM_ERROR,
                             "can'(%P|%t) t register with reactor\n"),
                            -1);

        ACE_DEBUG ((LM_DEBUG,
                    "(%P|%t) connected with %s\n",
                    addr.get_host_name ()));

        return 0;
      }

      /* This is a matter of style & maybe taste.  Instead of putting all
        of this stuff into a destructor, we put it here and request that
        everyone call destroy() instead of 'delete'.  */
      virtual void destroy (void)
      {
        /* Remove ourselves from the reactor */
        g_reactor->remove_handler
          (this,
           ACE_Event_Handler::READ_MASK | ACE_Event_Handler::DONT_CALL);

        /* Cancel that timer we scheduled in open() */
        g_reactor->cancel_timer (this);

        /* Shut down the connection to the client.  */
        this->peer ().close ();

        /* Free our memory.  */
        delete this;
      }

      /* If somebody doesn't like us, they will close() us.  Actually, if
        our open() method returns -1, the Acceptor<> will invoke close()
        on us for cleanup.  */
      virtual int close (u_long flags = 0)
      {
        /* The ACE_Svc_Handler baseclass requires the <flags> parameter.
          We don't use it here though, so we mark it as UNUSED.  You can
          accomplish the same thing with a signature like handle_input's
          below.  */
        ACE_UNUSED_ARG (flags);

        /*
          Clean up and go away.
          */
        this->destroy ();
        return 0;
      }

    protected:

      /* Respond to input just like Tutorial 1.  */
      virtual int handle_input (ACE_HANDLE)
      {
        char buf[128];
        ACE_OS::memset (buf, 0, sizeof (buf));

        switch (this->peer ().recv (buf,
                                    sizeof buf))
          {
          case -1:
            ACE_ERROR_RETURN ((LM_ERROR,
                               "(%P|%t) %p bad read\n",
                               "client logger"),
                              -1);
          case 0:
            ACE_ERROR_RETURN ((LM_ERROR,
                               "(%P|%t) closing log daemon (fd = %d)\n",
                               this->get_handle ()),
                              -1);
          default:
            ACE_DEBUG ((LM_DEBUG,
                        "(%P|%t) from client: %s",
                        buf));
          }

        return 0;
      }

      /* When the timer expires, handle_timeout() will be called.  The
        'arg' is the value passed after 'this' in the schedule_timer()
        call.  You can pass in anything there that you can cast to a
        void*.  */
      virtual int handle_timeout (const ACE_Time_Value &tv,
                                  const void *arg)
      {
        ACE_DEBUG ((LM_DEBUG,
                    "(%P|%t) handling timeout from this = %u\n",
                    this));
        return 0;
      }

      /*
        Clean ourselves up when handle_input() (or handle_timer()) returns -1
        */
      virtual int handle_close (ACE_HANDLE,
                                ACE_Reactor_Mask)
      {
        this->destroy ();
        return 0;
      }
    };

    #endif /* LOGGING_HANDLER_H */

[Tutorial Index] [Continue This Tutorial]