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If multiple clients advise themselves with the server, the code that the Wizards generate (the 'CProxyDHelloWorldEvents' class) already takes care of that.
In effect, the Fire_OnSayHello() function, as you can see in the HelloServCP.h file, runs a little for( ) loop to call all the clients that have Advised() the server. If multiple clients Advise the server, then when the server fires an event (by calling Fire_OnSayHello( )), all clients will receive the event.
Try this:
1. Put the server (the HelloServ.exe and HelloServps.dll files) on the server machine,
and then copy the client program to more than one machine. Also, don't forget to put the HelloServps.dll file on each client machine and register the DLL on both machines. In fact, you need to copy HelloServ.exe to both and register it on both, because otherwise AfxConnectionAdvise() will fail.
2. Click the Start Server and Advise Server button on both, and then click the Call Method button on one of them... I would be interested in hearing about what happens!
Bria
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When I Click the "Start Server" button, I got a message
saying "Unable to access IHelloWorld because Class not Registered",. I am creating the server locally, by un-comment the this line /*HRESULT hResult = m_pHelloWorld->CreateInstance(CLSID_HelloWorld) */
I did registered the HelloServ.dll with regsrv32.exe. I would be greate if you can let me know what could cause this problem.
Thanks in advance.
Camso
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You also need to run 'HelloServ /RegServer' on your local machine in order for local creation to work. See Step 6 for more details.
1. Run 'HelloServ /RegServer'
2. Run 'regsvr32 HelloServps.dll'
And voila! Let me know if you continue to experience problems.
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Hello readers...
I have received questions from people and I wonder if you are starting from the beginning and working through the tutorial. I provide detailed (I hope  ) guidance to you throughout the tutorial, and we go through the process in a step-by-step manner, so as a tip, I suggest that you start out at Step 1 before you post and tell me my tutorial doesn't work or you don't understand it.
Brian Har
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You don't state what the readers should already know in order to follow all this (ATL, COM, MFC's COM, etc.)
Playing around with wizards really doesn't accomplish much when it comes to something as complicated as COM/DCOM. You really should do much more explaining. Sadly, your tutorial is typical of many computer books. At least your stuff is free!
Since many folks don't have two computers, you should explain how to configure this as a local server. This is a good debugging technique anyway.
I was unable to get steps 6 & 7 working on a single machine, and I don't have time for debugging. Your description of step 7 leaves out ALOT of the steps needed
to recreate the client code, so it has to be copied from the zip file.
I would've used ATL's implmentation of connection points on both the client and server. Its more consistent and understandable
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Steve,
Thanks for getting back to me! If you look on Step 1, I do explain what you need to know to follow the tutorial, and I do my best to explain things where appropriate (see Step 5 for Connection Points). I like to think that sometimes we need a I-don't-care-how-this-works-just-how-do-I-do-this tutorial for complex things like DCOM, kind of like the remote control.
I do appreciate your suggestion about making the tutorial more comprehensive and accounting for different reader configurations. I plan to write other, more comprehensive tutorials as things progress along. I know you're frustrated because of what I do have and things not working, and I want to do my best to fix this Please bear with me -- using the Visual C++ wizards is something alot of people just starting out are comfortable with, too, so that's why I used this approach. Step 7 does need to be more comprehensive, though, I agree.
Watch for updates!! And try to begin this tutorial on the first step, Step 1, if you haven't. It's something that I always recommend
Plus, about using ATL's implementation of Connection points -- they're an option, but Microsoft didn't explain how to use them without putting a lot of docuemntation to wade through in my face Plus, Connection Points in ATL don't actually work consistently, whereas the MFC implementation is a little more robust
Cheers,
Brian Har
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Ya, I went through all the steps, but based on the meager descriptions, it seems readers were expected to know than what you listed in Step1.
I'm sure you know there's lots of example code & wizard tutorials on the web, what's lacking is good descriptions of the technologies that don't mimic MSDN. There are also tools that can be discussed to help beginners get a better understanding & fix problems (RegEdit, the Services Control Panel applet, etc.).
The wizard issue is really one of philosophy. If, under blue sky conditions, the tutorial does exactly what someone needs - GREAT! If, however, slight changes need to be made or someone makes a small mistake that somehow compiles, there could be alot of frustration.
I've been using both MFC's & ATL's implementations of connection points for several years, and I prefer ATL's. I don't know of anyone who prefers MFC, except for those I-don't-want-to-learn-the-basics-of-COM types (wizard people). Wizards per se are OK, but only with some understanding of what they're doing.
Actually, the whole event thing changes with COM+, but that's another tutorial!
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Steve,
Don't knock the Wizards, man!
Seriously, though, I totally agree with you on many levels, and I think you make some very valid points. Especially that, no, this tutorial doesn't do crap! But that's not the point. The point is to teach by trivial example; if you have your hand held to do something simple, chances are it makes doing something else that's more complicated a little less daunting.
I'm not stopping you from writing your own tutorial if you think you have a different if not better approach. In fact, I wouldn't miss it for all the tea in China! (Apologies to Chinese readers of this site) By all means, explain to us, Great Guru...
It's just that, I spent time out of my work schedule and life to write the tutorial... And tutorials are not around to do 'exactly what people need' anyway... they teach, (hopefully) or they don't.
Please note that I didn't have to post anything at all on The Code Project and could have saved time maybe... This tutorial's purpose never was to show you why or how DCOM/COM/ATL works, but just to do the most simple procedure I could think of so people can have chances to 'get their feet wet' as it were...
Of course you don't need the Wizards, but for some of the enormous amounts of code that one has to write and that you have to do some of it every time regardless of the software you're writing, they do save some typing and leave to worry about what you're going to write instead of how to write it...
But seriously, why make things unnecessarily hard and go to effort that you don't have to go to when there are tools that make it easier and faster to meet your deadlines (and maybe even, shudder, impress one's boss...).
"If someone makes a small mistake or there are changes in the code that somehow compiles, there can be a lot of frustration," Whoever said frustration wasn't a natural part of programming?? Plus, to address your point about "Wizards are OK, but only with some understanding of what you're doing," That's a valid point and I totally agree Don't you see? If I can just use wizards to write the framework for me, fill in the details, and voila!, working program in two weeks instead of spending one month or more on the learning curve and then coding everything from scratch, you can guess which route I'm going to take
If someone had posted this tutorial up earlier this summer than I did, I probably could have gotten way more done in less time by just having the educational experience of doing these basic steps... by doing this one learns more in less time and even gains understanding!
But hey, we could bandy this back and forth forever like the whole Windows vs. UNIX/LINUX/KOBOL (and COBOL) debate.
You program with what you prefer, and I'll program with what I prefer, and let's call it Pax, OK?
Plus, how about, since you champion ATL's implementation of connection points so much, then write up a similar tutorial that implements the same "Hello World" client and server but with more ATL than MFC... Because to tell truth, I am stumped by the ATL way, and if you have insight I definitely think that would be useful to not only me but also other readers of The Code Project.
C'mon, explain to us how it should be done; no one's stopping you!! However, no crapping on my work -- if you have criticisms be fair and constructive with your words. It doesn't look good to stomp all over someone else's work... But I can take appropriately and diplomatically worded criticisms...
Sincerely Yours,
Brian Har
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I would like to say many THNX  to Brian. I didn't had a lot of time to learn DCOM, but this example helped me to finish my job in time.
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There are always different ways to reach a goal.
I.e. you can take the pony express or an airplane.
For me it would be the plane (wizards!!!), but why
not letting others use the good old pony express.
Thanx for your great tutorial.
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Steven,
I too would like to see this implemented in ATL. Please write a similar article using ATL instead so we can all learn. It would be especially nice to include why the ATL is better than the MFC implementation.
Thanks,
Ed Evans
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Another vote for the ATL based copy of this tutorial.
Cheers,
Milan
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It seems to be a nice learning while reading this article.
How can I use it on windows98,I do have Visual Studio6
,DCOMCNFG.EXE,ATL.Please do reply fast.thank
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Microsoft has a patch for Windows 98/95 called DCOM98. I say in the article that you can get this at the Microsoft site, at http://www.microsoft.com/com/.
Look for a "DCOM98" folder or file with the Find File command on the Start menu, and then install that puppy.
Cheers,
Brian Har
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Please note that in Step 1 I tell you what this tutorial assumes:
+ ...
+ ...
+ That you're developing all this on Windows NT 4.0 or higher
Give the Microsoft DCOM98 extensions a try and see if they work. Check out http://www.microsoft.com/com/ for more, too.
Cheers, Bria
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Is enabel testing on computeruse in each different server
how..............
i. change to server name xxx.xxx.xxx.xxx
2. i remake it
but!! do not playing
how..............
i'm very cry
please tell me please...oh~please hot!!
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You must put L"021.120.402.302" (the IP number is just an example) in to the serverInfo.pwszName member. If you're trying to do
serverInfo.pwszName = 127.0.0.1 it doesn't work. It must be
serverInfo.pwszName = L"127.0.0.1
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unable to acess IHelloWorld becuase do not access.
what's mean?
i don't know.....Y_Y
please help me teacher.
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I'm sorry; I know you're trying your best. I can't understand what you're saying...
Do you get E_ACCESSDENIED returned from CoCreateInstanceEx()?
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I have question related to the security problem.
The only way I know to find something about the caller is to use IServerSecurity methods.
Is there any other way to find who is the caller or this is the only one method
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I don't know too much about security; wish I did though. I would say that the IServerSecurity and IClientSecurity interfaces are pretty much the safest and most standard ways of doing things.
Remember, in this tutorial, we call CoInitializeSecurity() like we do so that we can test without pesky 'Access Denied' messages coming up all of the time.
Hope I was of any help!
Cheers,
Brian Har
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When I disconnect some clients ( advised to DCOM server ) by disconnecting the cable or by a "GPF" error generate by the operating system ( unadvised method wasn’t called )
in call Fire_xxxx function I quit from Invoke function after Time out. It mean that the rest of the clients not received the event immediately.
Can I solve this problem? I'll appreciate your assistance, by sending me some relevant examples, if u had any ?.
Regards
Igor Lisbaron.
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hi!
this is a nice tutorials but....
how can i remote test......
hm..
please help me to super man ~~m(^_^)m~
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NOTE: If you read this, and would like to see this put on the main Questions and Answers page, let me know at brian@harttechservices.com and I will do it if there's enough interest
To answer your question:
Go to Step 7, and look at the code for my OnStartServer() function.
Look at where I fill in the members of COSERVERINFO:
"serverInfo.pwszName = L"\\\\Viz-06";"
As you know, this tells the client my server is on \\Viz-06. This is an UNC, or network, name for the server machine.
Now, \\Viz-06 is on the lcse.umn.edu domain on the Internet. It isn't a Web server, but it has the HelloServ DCOM server on it; if I wanted to test my server with my client from home, I would have put in
'serverInfo.pwszName = L"viz-06.lcse.umn.edu";'
Specifying hosts in DCOM works three ways; you can use:
1. A wide string literal (for example, L" ") containing the network name, like \\Viz-06;
2. An Internet name, in a wide string literal, like L"viz-06.lcse.umn.edu"
3.Or a dotted-decimal IP number in a wide string literal, such as L"127.0.0.1".
Hope that works! See Step 6 for how to build and install our server, and then go to Step 7 and see how to work with the client.
NOTE: DCOM likes to use TCP/IP, but if you are using the client on a computer with dial-up Internet access, make sure to dial in to your provider before using the client. Also note that the DCOM calls take longer over such a connection.
Cheers
Brian Har
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