Open Multiple Internet Sessions

Posted on 2000-04-09
Last Modified: 2013-11-20
Working With NT, VC6.

I Opened 100 threads
and In Each Thread opened an Internet session.

CInternetSession MySession;
pFile = MySession.OpenURL(url);

I See that 100 threads are running
but somehow in every moment only 2 Sessions are really working.

It seems that NT closes the session whenever it wants...

(I`m using 'netstat' from command prompt)

How can I really open 100 sessions
at the same time?


int LoadURL(const char* url,char* buffer,int bufferSize)
  CInternetSession MySession;
  CStdioFile* pFile = NULL;

   pFile = MySession.OpenURL(url);
   while (pFile->Read   (buffer,bufferSize) > 0)
     //read file...
   delete pFile;

Question by:TelMic
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LVL 11

Accepted Solution

mikeblas earned 50 total points
ID: 2698199
100 threads?  That's absolutely silly; you're wasting more time than you're actually getting work done.  If you've used the default stack size, 100 threads is going to take 100 megs of memory--and that's going to leave you swapping all over the place, unless you have more than 256 megabytes of memory.

Please reconsider your design: you need to do things that will work, and work right--not just throw threads at the problem.

Anyway, that that your client only lets two threads run is completely by design. WININET.DLL is implemented per the HTTP specification, which stipulates that a client should only have two active sessions open against any given server at any time. That's to avoid the client from overpowering the server--something you're bound to do if you ever get those 100 threads of yours running efficiently.

I'm loathe to tell you this because, given your use of 100 threads in your app, you're doubtlessly going to abuse it. But you can hack the registry to get around the limit.

For connections using  HTTP/1.0, you should set the DWORD at HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\InternetSettings\MaxConnectionsPerServer . And for connections using HTTP/1.1, you can set the DWORD at HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\InternetSettings\MaxConnectionsPer1_0Server REG_DWORD (HTTP/1.0 limit) .

Note that this setting effects _all_ apps that use WININET and not just your app, so it's possible you'll break something else on your system by changing the setting.

..B ekiM
LVL 11

Expert Comment

ID: 2698203
Why in the world do you sleep 10 seconds after opening the URL?

..B ekiM

Author Comment

ID: 2705324
thanks mikeblas,


The only problem is that I get
Sometimes InternetException with Error Code 12002 and others how can I know what does any Error Code Mean...
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LVL 11

Expert Comment

ID: 2705997
> how can I know what does any Error Code Mean...

Use the ERRLOOK tool.  It's in the Tools menu in the Visual C++ IDE, and it's installed to be on the path after you setup VC++.

Or, use the ReportError() or GetErrorMessage() member functions of CInternetException.

..B ekiM

Author Comment

ID: 2709448
GetErrorMessage() is not a member
of CInternetException
LVL 11

Expert Comment

ID: 2710264
> GetErrorMessage() is not a member
 > of CInternetException

I'm sorry, but it is. I know it is because I'm the one who added it to MFC. If you're using Visual C++ 6.0, see line 2754 of INET.CPP in the MFC\SRC directory.

..B ekiM

Author Comment

ID: 2722362
The Error I get is "The operation is timed out",
because I`m sending a lot of request,

Is there is any way to change the TimeOut for OpenURL()?

LVL 11

Expert Comment

ID: 2729054
Yes. Before calling OpenURL() on the session, call SetOption() on the session object. Use these options to set the time out parameters:


Read the docs to learn what they do; some are meaningful only for cetain protocols. But they're all local to your session, so it's not as if you'll harm another program by changing them.

Please also read Knowledgebase Articles Q224318 and Q176420.

..B ekiM

Author Comment

ID: 2741882
Thanks a lot!

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