Re: WinSock SendData -> unknown Exception

clinisbut <>
Wed, 20 Feb 2008 00:59:36 -0800 (PST)
On Feb 19, 6:11 pm, Joseph M. Newcomer <> wrote:

On Tue, 19 Feb 2008 00:24:59 -0800 (PST), clinisbut <> =


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 wouldn't use

anything more sophisticated than a SetTimer() call.

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


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

thread, and never

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

 created it.



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

m> wrote:

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


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

he callback occurs in

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

allback really is called

in a separate thread.


On Mon, 18 Feb 2008 04:08:00 -0800 (PST), clinisbut <clinis...@gmail=> wrote:

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


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 objec=

t? 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 "Firs=


chance exception in XXX.exe (MSWINSCK.OCX): 0xC0000005: Access

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


I found that program crashes in function (called automatically from=


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

, va_list

           SCODE sc = m_lpDispatch->Invoke(dwDispID,=

 IID_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 c=

har> out_tcp;

                      //fead out_tcp with da=


                   Send_TCP( out_tcp ); <-=

-This 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?

If youare not using a multimedia timer to manage your communication, why d=

id you say

I'm having another trouble and is happening when I call the same
function from a multimedia timer.

That sounds to me like you are calling your serial communication object fr=

om some other


If you are using a mmtimer to send a message to the main GUI thread, why n=

ot just use

SetTimer/WM_TIMER to handle it? (note: there may be a valid reason, but I =

want to hear

from you why you decided not to use a multimedia timer instead of a simple=


Joseph M. Newcomer [MVP]
MVP Tips:

Should be my bad english that causes this missunderstoods... I'm going
to try to explain better:

The multimedia timer is used MAINLY to send a frame through serial
comm. But there is a chance some condition to happen and then I need
to send a socket to client. Just that. That's the only reason I need
to send a socket from that MMtimer.

The main "handler" of sockets is in the GUI thread and no problems
with that.
Maybe should I send a message from MMTimer to GUI thread to send that

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