?
Solved

Accept and Multi-Threading problem!!!

Posted on 1998-12-28
10
Medium Priority
?
233 Views
Last Modified: 2013-11-20
hi folks,

    I am building a server application using CSocket class and threads. In my server app, I create a child thread (worker thread) to handle connection (Accept()) and network I/O (infinite loop). I also create a  exit message handler to closes all network connections. Whenever I click the exit button on my server app, my program crashed. Why?? Any solution??

stephen
 
0
Comment
Question by:stephenkong
10 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 1326835
Do you synchronize the access to the CSockets between the threads and the message handler?
0
 

Expert Comment

by:yoffe
ID: 1326836
Adding to jkr's response, is the worker thread accessing any objects that are created by another therad (stack or heap).   If so, when your primary (MH) thread dies and destroys those objects, access violation...game over.
0
 
LVL 3

Expert Comment

by:shaig
ID: 1326837
While the win32 api is thread safe, MFC isn't. You should sinchronize all access to MFC objects yourself.
0
Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 86

Expert Comment

by:jkr
ID: 1326838
>>While the win32 api is thread safe...
shaig, i wish it was! ;-)
(just try 2 threads accessing one GDI object without synchronization...)
0
 

Expert Comment

by:koskia
ID: 1326839
My program Crash answer !??

add some code, maybe this will help ?!
0
 
LVL 3

Expert Comment

by:shaig
ID: 1326840
Using handles?  Well if you say so i'll take your word for it. When you think you saw it all, Microsoft come and...
0
 
LVL 86

Expert Comment

by:jkr
ID: 1326841
shaig - it is so. Somewhere deep in the docs they state that the GDI isn't sync'ed due to performance issues ;-)
0
 

Author Comment

by:stephenkong
ID: 1326842
hello folks,

   My worker thread was executing CSocket::Accept() while I was pressing the Exit button.

   In the 'Exit' message handler:
{
// This variable is useless since worker thread was stuck in
// CSocket::Accept()
   m_bIsFinished = TRUE;  // bool variable to break the infinite
                          // loop inside the worker thread
   Sleep(300);    
   sock.Close();
   PostQuitMessage (0);
}
0
 
LVL 7

Expert Comment

by:faster
ID: 1326843
When the main thread close the socket of worker thread, if the worker thread is still using the thread and error handling is not carefully done, this might happen.
0
 
LVL 2

Accepted Solution

by:
jonalee earned 150 total points
ID: 1326844
Please do not use CSocket::Close() directly. Use Shutdown(2) first. Then overide the CAsyncSocket::OnClose(int). In that function, call Close() after CAsyncSocket::Close() is called.

Also, if the coding you give out is in the Thread, please use PostThreadMessage(WM_QUIT,0,0L)


0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction: Load and Save to file, Document-View interaction inside the SDI. Continuing from the second article about sudoku.   Open the project in visual studio. From the class view select CSudokuDoc and double click to open the header …
Introduction: Dialogs (2) modeless dialog and a worker thread.  Handling data shared between threads.  Recursive functions. Continuing from the tenth article about sudoku.   Last article we worked with a modal dialog to help maintain informat…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
There may be issues when you are trying to access Outlook or send & receive emails or due to Outlook crash which leads to corrupt or damaged PST file. To eliminate the corruption from your PST file, you need to repair the corrupt Outlook PST file. U…

601 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question