Re: Still the same: CAsyncSocket::Receive and CAsyncSocket's threading

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Tue, 09 May 2006 10:00:39 -0400
MiSo wrote:

I red all messages, about CAsynchSocket and threading and also Mr
Newcomer mvp_tips. And still my problem persist.

Shortly I've problem with client socket.
My dll library implements protocol to some server. I'm using CAsyncSocket.
Dll must be using from dot.Net framework and when I use it simple by
calling functions from dll all works fine.
But when I create thread and thees all functions are called from thread
function OnReceive is not fired.

myThreadFunction {


  while ( canrun ){

In my case ConnectToServerDll - should cause that server sends data to
In example above I receive no data but when I add
MessageBox.ShowModal(); ->
myThreadFunction {

  while ( canrun ){

I receive data.

Can someone explain this behavior?

I TRACE all functions and I print ThreadID. I see all my operations on
dll are in the same thread. Then I think that I don't need to deattach
and attach SOCKET.

Mirek Sobczak

Using the while(canrun) loop in your thread causes the problem. If your
thread is executing the while loop it is not executing the MFC message
pump. OnReceive comes from the MFC message pump.

MessageBox executes a message pump. That's why it seems to fix the
problem: It lets messages come in.

If your thread is a worker thread then you have a second problem. A
worker thread does not provide a message pump. You must use
CAsyncSocket in a thread that contains the MFC message pump. (Derive a
class from CWinThread to make an MFC "UI" thread.) Then your thread
code must return to MFC after every call to Connect or Send or Receive.
  That returns to the MFC message pump so it can call
CAsyncSocket::OnReceive when data is received.

Scott McPhillips [VC++ MVP]

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