Re: WinSock SendData -> unknown Exception

clinisbut <>
Tue, 19 Feb 2008 00:24:59 -0800 (PST)
On Feb 18, 6:50 pm, Joseph M. Newcomer <> wrote:

I would not use a timeSetEvent callback to handle socket communication. =

 Because there

should be no serious time constraints for TCP/IP or UDP communication, I w=

ouldn't use

anything more sophisticated than a SetTimer() call.

Note that you *can* use a socket in a separate thread (see my essay on mul=


sockets), but it involves giving complete control of the socket to the thr=

ead, and never

again using the socket from any other thread, including the thread that cr=

eated it.



On Mon, 18 Feb 2008 07:52:23 -0800 (PST), clinisbut <> =


On Feb 18, 4:31 pm, Joseph M. Newcomer <> wrote:

It turns out that the timeSetEvent documentation does not say that the =

callback occurs in

a separate thread. This is a documentation failure, because the call=

back really is called

in a separate thread.


On Mon, 18 Feb 2008 04:08:00 -0800 (PST), clinisbut <

m> wrote:

On Feb 16, 2:00 am, Joseph M. Newcomer <> wrote=


I question the fundamental decision to use an ActiveX control to do =

something as simple as

socket handling. I believe the control does synchronous I/O.

Yeah, sure! but does another issue...

Could you report ALL the values of the COleDispatchException object? =

 Most especially the

m_wCode = 0

I think that's the only value I've left behind.

I'm having another trouble and is happening when I call the same
function from a multimedia timer. But this time I'm getting a "First
chance exception in XXX.exe (MSWINSCK.OCX): 0xC0000005: Access

I think it has to do with the variant type. Debugging this last error,=

I found that program crashes in function (called automatically from

  void COleDispatchDriver::InvokeHelperV(DISPID dwDispID, WORD
wFlags, VARTYPE vtRet, void* pvRet, const BYTE* pbParamInfo, v=


           SCODE sc = m_lpDispatch->Invoke(dwDispID, II=

D_NULL, 0, wFlags,

&dispparams, pvarResult, &excepInfo, &nArgErr); //<---This is where
error occours!!!

Maybe has something to do with MMTimer? this is how I implement it:
void CALLBACK CUart3Dlg::StartTimer( UINT wTimerID, UINT msg, DWORD
dwUser, DWORD dw1, DWORD dw2 )
   CUart3Dlg* obj = (CUart3Dlg*) dwUser;
       obj->Timer_SendData( wTimerID );

void CUart3Dlg::Timer_SendData( UINT wTimerID )
   if( buffer_out.size() > 0 )
           if( ui_retry_counter<MAX_RETRY_COUNT )
                   //Some operations
                      std::vector<unsigned char=


                      //fead out_tcp with data
                   Send_TCP( out_tcp ); <--Th=

is calls my m_Winsock.sendData( v );


Joseph M. Newcomer [MVP]
MVP Tips:

So will have similar problems using CAsynsocket?? What you suggest
then to work with sockets?

Joseph M. Newcomer [MVP]
MVP Tips:

I don't use MMTimer to manage socket communication, but serial comm.
Every X ms I'm sending a frame through serial, and if a specific
condition is true before that sending, I send a socket to a client
informing that "problem". That's 'cause I use MMTimer, to control
frame sending to serial comm.
Maybe when this condition is true could I send a message to main GUI
thread to send that socket?

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