COM Discussion Boards

Henrik Sternberg24-Jan-02 1:45

24-Jan-02 1:45

Not knowing exactly what you are doing, it sounds as if the integer datatype is different between the client and the DCOM server. What kind of client are you using?

I have had this problem and I solved it by using the BSTR datatype. To do "pure COM" and being on the safe side, you should always pass BSTR:s as parameters, since they will be the same on both client and server side. This leads to a bit more of converting, but that's life Wink | ;)

Best regards,

/_henrik

Henrik Sternberg,
Cambridge Technolgy Partners, Germany
www.ctp.com/ce

henrik.sternberg@ctp.nospam.com
(take away nospam)

Does the number of events affect Performance ??

Firoz17-Jan-02 19:00

Firoz

17-Jan-02 19:00

Hi,

I have a DCOM application, where the component fires 8-10 events.
But all the events are similar in structure. (ie. they doesnt have any data associated with them).
The only difference is the event name.

So, I can easily use a single event to Notify all my events to
the client (And have some Parameter that distinguishes the event
to the client).

Now, my question is will this (using a single event in place of many events)
provide any PERFORMANCE benefits in a DCOM application ??

if yes, How ?? (some technical description will be appreciated)

anyway, the number of Network RoundTrips is going to be the same...

if no,
What will be a good COM programming practice in this situation.
(using a Single event or using different events)

Please somebody reply ... Frown | :(

I had posted this earlier, but got no response...

Thanks,

Firoz.

Re: Does the number of events affect Performance ??

Not Active18-Jan-02 2:42

Not Active

18-Jan-02 2:42

From a mantainability and debugging point of view combining all events into a single one would of course be more beneficial.

I don't believe I've seen any performance difference in using multiple events rather than a single one, as you said the round trips will be the same.

Re: Does the number of events affect Performance ??

Jamie Hale22-Jan-02 8:54

Jamie Hale

22-Jan-02 8:54

Firoz wrote:
the number of Network RoundTrips is going to be the same...

How do you figure? As I see it, DCOM needs to setup for each call. If you only call once, this setup (marshalling and whatnot) is only done once. If you do many calls, this setup needs to be done each time. Sure the amount of data (from your point of view) being sent is the same (1 x 10 events or 10 x 1 events), but I think you need to take into consideration the setup and teardown of the connection.

Please correct me if I'm wrong. Smile | :)

BSTR

newbe17-Jan-02 2:10

newbe

17-Jan-02 2:10

Hello, can somebody please help me:
i'm trying to write a string to a file serverside. and i want to get the string back. So i use the next function:
MIDL :write [in]BSTR message
cpp: HRESULT Write(BSTR message)
{
//code to write to a file on the server
}
can u please explane how the BSTR type works and how can i convert it to a normal string

Re: BSTR

Carlos Antollini17-Jan-02 2:38

Carlos Antollini

17-Jan-02 2:38

CString str = _T("")
str = message;

Carlos Antollini.
Sonork ID 100.10529 cantollini

Re: BSTR

Not Active17-Jan-02 5:28

Not Active

17-Jan-02 5:28

CString str(message)

Re: BSTR

Ernest Laurentin17-Jan-02 5:26

Ernest Laurentin

17-Jan-02 5:26

One of the easiest way to use the BSTR type as normal string, in my opinion is
to use the compiler string type: _bstr_t
Use like this:

HRESULT Write(BSTR message)
{
 _tprintf(TEXT("Message:%s\r\n", (LPCTSTR) _bstr_t(message));
}

You can look at the description for _bstr_t in MDSN for more help.
It can also convert ASCII string to Unicode. You may want to use conversion macro.

HRESULT Write(BSTR message)
{
USES_CONVERSION;
LPCTSTR lpszNormal = OLE2CT(message);
 _tprintf(TEXT("Message:%s\r\n", (LPCTSTR) lpszNormal);
}

Re: BSTR

Not Active17-Jan-02 5:29

Not Active

17-Jan-02 5:29

CComBSTR

Re: BSTR

pba_24-Jan-02 7:17

pba_

24-Jan-02 7:17

MultiByteToWideChar / WideCharToMultiByte or mbstowcs / wcstombs Wink | ;)

Re: BSTR

yamini13-Feb-02 1:14

yamini

13-Feb-02 1:14

There are 2ways to do this
The first method uses the OLE2T() for BSTR conversion to string.

The second method uses _bstr_t for conversion.
******************************************************#inclu#include <iostream.h>
#include <atlbase.h>
#include <comdef.h>
void main()
{
BSTR b=L"StringConversion"; //BSTR string
USES_CONVERSION; //First method of Conversion
cout<<"String :"<

Events in MFC client

Member 1697717-Jan-02 1:26

Member 16977

17-Jan-02 1:26

Hi,All
I have a component(built using ATL) which supports outgoing interfaces.I want to use this component in MFC client.
When component fires an event i want to trap it and show the string which it sends in the modeless dialog box.
I dont know how to trap events in MFC client.
Can anybody help.
Regards
Tushar

Re: Events in MFC client

Prem Kumar19-Jan-02 10:58

Prem Kumar

19-Jan-02 10:58

Look at the MSDN KB article Q181845.
"HOWTO: Create a Sink Interface in MFC-Based COM Client".

regards,
Prem

Re: Events in MFC client

Matt Philmon13-Feb-02 17:51

Matt Philmon

13-Feb-02 17:51

Let me know if you get really stuck. Connection Points are just as unbelieably hard to handle in MFC applications as they are easy in VB. I can give you some details or examples if you need it.

Deleting mutiple instances of COM object

Ebin16-Jan-02 20:01

Ebin

16-Jan-02 20:01

We have implemented a com client in VC++ and it should communicate with server that developed in Delphi(.dll).

The Scenario is as folows
-------------------------------------

A button click on com client(vc) will invoke the com server (Delphi interface)(dialog based).
which will display a dialog were user can interact.Thus by the button click on VC client(dialog based) can invok multiple instances of delphi server.

Now we need to delete or close all the instances of com server with a single click in vc client (com client)
how it is possible ?.

Thanks in Advance
eby

Re: Deleting mutiple instances of COM object

Henrik Sternberg18-Jan-02 1:02

Henrik Sternberg

18-Jan-02 1:02

Hello Eby,

What kind of server is it? (IN/OUT of process)

Can you provide more details?

Regards,

/_henrik

Henrik Sternberg, Consultant
Cambridge Technolgy Partners, Germany
www.ctp.com/ce

henrik.sternberg@ctp.nospam.com
(take away nospam)

Re: Deleting mutiple instances of COM object

Prem Kumar19-Jan-02 11:03

Prem Kumar

19-Jan-02 11:03

Hi,

Since the Client invokes the server application,
u could have a the interface pointers stored in a
list and close all of them when ever u want to.

But this sounds probably too easy or may be i am not
aware of any additional details where u r facing problems
but from ur q's these should work.

regards,
Prem

GIT in Worker Thread Crashes

16-Jan-02 6:42

Hi, I'm creating a worker thread in my ATL Object, and all the events seem to be getting handled right at the end. This has happened with many other people, and there are plenty of "What to do's" but not "How to do it".

So i'm trying to use a GlobalInterfaceTable which supposedly is the easiest and i'm trying it "last" (hoping this will be the last).. i tried using CoMarshalblahblah() but it still does the same thing w/o using those functions by just passing object through the LPARAM of CreateThread().

So anyways, it crashes in OLE32.exe when i call GetInterfaceFromGlobal(). It seems to get the Cookie fine and everything, but... when that function is called... it crashes.. and i dont know what i'm doing wrong... it's really frustrating cuz i've worked on this for a LONG TIME... Dead | X|

so I think some source sample would be awesome. a few things:

********
# Where do i call CoCreateInstance() & GetInterfaceInGlobal()? From the function that creates the thread or from inside the thread? (i assumed it would be in my Function that creates the thread.

# I only have one of these objects right at the moment, so i just made the DWORD g_dwCookie "global", and I was passing the GIT through the LPARAM of CreateThread() and then calling
GetInterfaceFromGlobal(cookie, IID_ISpyder, (void**)Spy);
*for the record Spy is just a ISpyder *Spy = NULL; that's ok right?

Coolio, anyone lemme know if you can help me! Source or advise is cool! Thanks in advance!

~Timothy T. Rymer

www.digipen.edu
tim.xpertz.com

Re: GIT in Worker Thread Crashes

Joao Vaz16-Jan-02 7:44

Joao Vaz

16-Jan-02 7:44

Hi,

1- If you make the variable global why passing it in the LPARAM of createThread ?
Normally , or you make a variable global or you pass the variable thru the LPARAM.
2- Normally, with multiple threads in a process a guy must protect the data with a critical section or with another sinchronization stuff ...
3-It's necessary to call CoCreateInstance and RegisterInterfaceInGlobal on the apartment where the object lives
4- It must be GetInterfaceFromGlobal(cookie, IID_ISpyder, (void**)&Spy)), you forgot the ampersand Confused | :confused:

5-You can call RevokeInterfaceFromGlobal from any apartment, but you must be certain that is the last apartment that makes use of the interface pointer

Hope this helps, best of luck

Joao Vaz

Re: GIT in Worker Thread Crashes

Tim Rymer16-Jan-02 8:23

Tim Rymer

16-Jan-02 8:23

the only thing global is the cookie, i went ahead and made the GIT a member in my class, and passed it in through the LPARAM. but i didnt put my ampresand in there though. gonna try the stuff out now...

~Timothy T. Rymer

www.digipen.edu
tim.xpertz.com

Re: GIT in Worker Thread Crashes

Tim Rymer16-Jan-02 9:03

Tim Rymer

16-Jan-02 9:03

now when i call RegisterInterfaceInGlobal() - what should i pass in the first parameter? What do i do & How do i do it?

Do i just call QueryInterface? all i'm wanting is ISpyder but i'm in a CSpyder function... how do i do all that?

right now to get some kind of pointer, i call query interface and then pass an IUnknown *unk = NULL ---> (void**)&unk <--- into the function.

Thanks again..

~Timothy T. Rymer

www.digipen.edu
tim.xpertz.com

Re: GIT RegisterInterfaceInGlobal( )

Tim Rymer16-Jan-02 9:04

Tim Rymer

16-Jan-02 9:04

FINISHED!

Tim Rymer16-Jan-02 10:33

Tim Rymer

16-Jan-02 10:33

i got it working. who knows how, but if anyone else has this problem i can work with anyone now about it. i know what to do now. thanks a bunch.

~Timothy T. Rymer

www.digipen.edu
tim.xpertz.com

Re: FINISHED!

Joao Vaz16-Jan-02 22:35

Joao Vaz

16-Jan-02 22:35

Good for you Tim Rymer Big Grin | :-D

COM it's a beast to learn ,I readed 8 books on COM/ATL to be proficient

Regards and happy COM coding

Joao Vaz

How to set the identity user of a COM component

xicoloko16-Jan-02 2:28

xicoloko

16-Jan-02 2:28

Hi,

How to set the identity user of a COM component using VC++? Confused | :confused:

Thanks,
- xico -

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.