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diff --git a/docs/tutorials/002/page04.html b/docs/tutorials/002/page04.html deleted file mode 100644 index 5aae2b4205b..00000000000 --- a/docs/tutorials/002/page04.html +++ /dev/null @@ -1,271 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> -<HTML> -<HEAD> - <TITLE>ACE Tutorial 002</TITLE> - <META NAME="GENERATOR" CONTENT="Mozilla/3.01Gold (Win95; I) [Netscape]"> - <META NAME="Author" CONTENT="James CE Johnson"> - <META NAME="Description" CONTENT="A first step towards using ACE productively"> -</HEAD> -<BODY text = "#000000" link="#000fff" vlink="#ff0f0f" bgcolor="#ffffff"> - - -<CENTER><P><B><FONT SIZE=+2>ACE Tutorial 002<BR> -Creating a Better Server </FONT></B></P></CENTER> - -<P> -<HR WIDTH="100%"></P> - -<P>Since we've gone out of our way to make sure that the other parts of -the program are generic, you may expect that this final piece, the connection -handler, will be the most complicated. As usual, you are correct:</P> - -<UL> -<PRE>1. #include "ace/SOCK_Acceptor.h" -2. #include "ace/Reactor.h" - - -3. class Logging_Handler : public ACE_Svc_Handler<ACE_SOCK_STREAM, ACE_NULL_SYNCH> - { - - public: - -4. Logging_Handler (void) - { - } - -5. virtual void destroy (void) - { -6. g_reactor->cancel_timer (this); -7. this->peer ().close (); - } - -8. virtual int open (void *) - { -9. ACE_INET_Addr addr; - -10. if (this->peer ().get_remote_addr (addr) == -1) -11. return -1; -12. else - { -13. ACE_OS::strncpy (this->peer_name_, addr.get_host_name (), MAXHOSTNAMELEN + 1); - -14. if (g_reactor->register_handler(this, ACE_Event_Handler::READ_MASK) == -1) -15. ACE_ERROR_RETURN ((LM_ERROR, "(%P|%t) can't register with reactor\n"), -1); - -16. else if (g_reactor->schedule_timer (this, (const void *) this, ACE_Time_Value (2), ACE_Time_Value (2)) == -1) -17. ACE_ERROR_RETURN ((LM_ERROR, "can'(%P|%t) t register with reactor\n"), -1); - -18. else -19. ACE_DEBUG ((LM_DEBUG, "(%P|%t) connected with %s\n", this->peer_name_)); - -20. return 0; - } - } - -21. virtual int close (u_long) - { -22. this->destroy (); -23. return 0; - } - - protected: - -24. virtual int handle_input (ACE_HANDLE) - { -25. char buf[128]; -26. memset(buf,0,sizeof(buf)); - -27. switch( this->peer().recv(buf,sizeof buf) ) - { -28. case -1: -29. ACE_ERROR_RETURN ((LM_ERROR, "(%P|%t) %p bad read\n", "client logger"), -1); -30. case 0: -31. ACE_ERROR_RETURN ((LM_ERROR, "(%P|%t) closing log daemon (fd = %d)\n", this->get_handle ()), -1); -32. default: -33. ACE_DEBUG ((LM_DEBUG, "(%P|%t) from client: %s",buf)); - } - -34. return 0; - } - -35. virtual int handle_timeout (const ACE_Time_Value &tv, const void *arg) - { -36. ACE_ASSERT (arg == this); -37. ACE_DEBUG ((LM_DEBUG, "(%P|%t) handling timeout from this = %u\n", this)); -38. return 0; - } - - private: - -39. char peer_name_[MAXHOSTNAMELEN + 1]; - - }; -</PRE> -</UL> - -<P> -<HR WIDTH="100%"></P> - -<P>Here's the step-by-step explanation:</P> - -<OL> -<LI>This has no business being here but I refuse to renumber 38 lines of -source just to get rid of it.</LI> - -<LI>Come to think of it, this is probably not needed either. While we use -the global reactor object (<I>g_reactor</I>) througout this portion of -code, we don't actually create any new ones. Besides, we'll drop this code -into one file with <I>main</I> and <I>acceptor</I> and it won't matter.</LI> - -<LI>We've apparently decided to be bold and use yet another ACE template -to create our <I>Logging_Handler</I> object. From the manual, the <I>ACE_Svc_Handler</I> -template <I>defines the interface for a service that exchanges data with -its connected peer</I>. The first template argument specifies the kind -of connection we want to have. As mentioned on the previous page, this -<B>must</B> be compatible with the data type used to accept the connection. -As for the second argument, that's way beyond the scope of what we're -doing here. Just do it like you see it & we'll get around to explaining -that in a later tutorial. -to me.</LI> - -<LI>Our default constructor does nothing. We've moved anything with failure -potential into the <I>open</I> function. - -<LI>This should be called instead of <I>delete</I>. It will shut down the -object gracefully. The other choice is to have a very busy destructor and -you typically don't want that. Even better, if you make your destructor -protected then <i>delete</i> cannot be used on your object. Then they have -to go through <i>destroy()</i> to get rid of it! There are, of course, -down sides to that as well... - -<LI>Cancel any timer(s) which the reactor associates with this object</LI> - -<LI>Close the connection to the client. Notice that we use the <I>peer()</I> -member function generated by the template. We should never need direct -access to the actual connection object.</LI> - -<LI>The <I>open</I> function contains all of our initialization logic. -It is called by the acceptor when a new connection is accepted. If we fail -to initialize for any reason, we will return an error code so that the -acceptor can respond correctly. This could not be done in a constructor.</LI> - -<LI>Create a temporary variable that will hold the address of the client -system.</LI> - -<LI>Ask the connection object to give us the address of the client system. -This is something you will usually want to do for logging or validation -purposes whenever a new connection is received. See how easy it is?</LI> - -<LI>Tell the acceptor if we could not get the peer's address. Shouldn't -we have used <I>ACE_ERROR_RETURN</I>? You tell me.</LI> - -<LI>But, if the peer's address was gotten...</LI> - -<LI>Copy the peer's host name into a member variable. We could have simply -stored the address object but that has more information than we want to -keep around for a long time. Notice how the <I>ACE_OS</I> class is used -to access expected "normal" functions. While that may be a bit -of overkill, it does give us another level of abstraction from one platform -to another.</LI> - -<LI>As usual, we ultimately register ourselves with a reactor. Since we're -only interested in responding to the client's data, we only ask for <I>READ</I> -events to be sent to us.</LI> - -<LI>Another possible failure point...</LI> - -<LI>Just for giggles, we've decided to register a timer event with the -reactor also. As shown here, it will delay two seconds before firing the -first timer event and then be rescheduled every two seconds after that. -Timer resolutions of milliseconds can be used too!</LI> - -<LI>But, of course, any registration may fail.</LI> - -<LI>Everything must have worked if we got here</LI> - -<LI>so tell the driver about it</LI> - -<LI>and return success to the acceptor which invoked us.</LI> - -<LI>When we're asked to close ourselves, we first destroy the timer and -peer connection. It seems to me that we should do a <I>delete this</I> -at some point. Perhaps <I>destroy</I> should do that?</LI> - -<LI>Invoke the destroy method to clean everything up</LI> - -<LI>and return a success status.</LI> - -<LI><I>handle_input</I> is where you do whatever your application requires -when data is received from the client system.</LI> - -<LI>Create a storage space for the received data</LI> - -<LI>and make sure it is empty.</LI> - -<LI>Receive as much data as we can but don't overrun our buffer. For this -simple example, we don't get too fancy. In a real application we would -probably read some number of bytes (4?) and create a number from them. -We would then use that number to decide how many more bytes to read. The -number could be a simple byte count or it could be a packet type indicator -which implies a bytecount.</LI> - -<LI>If <I>recv</I> returns <I>-1</I> then there is something bad wrong -with the connection so</LI> - -<LI>we return an <I>-1</I> to the reactor along with a failure message. -We cannot continue after this.</LI> - -<LI>A <I>0</I> return from <I>recv</I> is not quite so bad. However, <I>handle_input</I> -wouldn't have been called if there was no data to be read. So, we take -this to be a sign that the client chose to shutdown the connection.</LI> -<LI>Like the case above, we need to return a <I>-1</I> to the reactor -so that we can be shutdown. </LI> - -<LI>Any other value from <I>recv</I> is taken to indicate the number of -bytes received so</LI> - -<LI>we display the data to the user. In the real world, we could do an -infinite number of things with the data.</LI> - -<LI>Return <I>0</I> if all is well with the receive so that the reactor -will allow us to continue functioning.</LI> - -<LI><I>handle_timeout</I> is something we haven't seen in any example so -far. Like <I>handle_input</I>, it is called by the reactor based on an -event. In this case, the event will be expiration of the timer we set in -the <I>open</I> function.</LI> - -<LI>It seems kind of silly for the handler to get a pointer to <I>this</I> -when the other handlers don't. Still, when given information of this type, -it is generally good to check it.</LI> - -<LI>Display a simple message to tell the user that we got the timer. In -your program, you may be expecting periodic data from your client. Simply -set a timer whenver you are through receiving data and cancel it whenever -you begin receiving it. If the timer handler is ever called, then you know -you didn't get data within the time you wanted.</LI> - -<LI>Returning <I>0</I> will tell the reactor to reschedule the timer as -configured in the <I>open</I> function.</LI> - -<LI>A simple string to hold the name of the client system. We could have -kept the entire <I>ACE_INET_Addr</I> object but we really only wanted the -name & not the extra baggage.</LI> -</OL> - -<P>Obviously this is a bit more complicated than the rest of the program. -Still, you see there isn't a lot of networking knowlege needed to get this -up and going. There are unfortunately several questions that I can't answer -(such as the <I>delete this</I> issue) but given time, I'm sure we'll all -figure it out.</P> - -<P> -<HR WIDTH="100%"></P> - -<CENTER><P>[<A HREF="..">Tutorial -Index</A>] [<A HREF="page03.html">Previous -Page</A>] [<A HREF="page05.html">Continue -This Tutorial</A>] </P></CENTER> - -</BODY> -</HTML> |