Re: WSAyncSelect in Multithreading

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Thu, 10 Aug 2006 07:57:56 -0400
Phanidhar wrote:

 I'm writing a win32 multhithreaded application which connects to a remote
machine on different threads.There is one socket connection per thread. Also
I'm using WSAAsyncSelect to receive the socket messages in my child thread's
message queue.

 The problem is that whenever I receive messages from remote machine, all
the calls in the messgequeue seems to be processed at once. That is my
processing code is executed concurrently. I was expecting it to be serialized
as the GetMessage() function would process the messages serially.MY code( for
child thread) looks something like this:



 switch ()
case WM_SOCkEVNT: //user defined meesge attached with WSAAsynSelect
   case FD_READ:

In the above context I would like to know the following
1) If I use WSAAsyncSelect in conjunction with multiple threads, is there a
possiblity that asynchronous socket notification itself will spawn a
execution context?
2)If I get multiple FD_READ evets, are they processed serially or each one
spawns a new execution?

 Thanking you in advance


It depends on your code. If your FD_READ processing simply saves some
data and returns then there will not be any reentry. But if, for
example, your FD_READ code executes a message pump (perhaps by calling
MessageBox) then recursive reentry into your WndProc can occur.

I don't understand your threading comments. Threading does not seem to
be relevant to your question. The socket message will only come in to
the thread that created the async select HWND parameter.

Scott McPhillips [VC++ MVP]

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