_REMOVING BLOCKING NETWORK I/O FROM WINDOWS PROGRAMS_
by George F. Frazier and Derek Yenzer


Listing One

BOOL TMainDialog::TransmitDoneMessage()
{
    HEADER_DATA  toTransmit;
    
    toTransmit.message = kchDoneMessage;
    if(m_CommunicationSocket.Send(&toTransmit, 
                                    sizeof(toTransmit)) != sizeof(toTransmit))
    {
        return(FALSE);
    }
    return(TRUE);
}  // TMainDialog::TransmitDoneMessage

BOOL TMainDialog::TransmitPixelMessage(LPPIXEL_DATA lpData)
{
    HEADER_DATA  toTransmit;
    
    toTransmit.message = kchPixelMessage;
    if(m_CommunicationSocket.Send(&toTransmit, 
                                    sizeof(toTransmit)) != sizeof(toTransmit))
    {
        return(FALSE);
    }
    if(m_CommunicationSocket.Send(lpData, 
                                  sizeof(PIXEL_DATA)) != sizeof(PIXEL_DATA))
    {
        return(FALSE);
    }
    return(TRUE);
}  // TMainDialog::TransmitPixelMessage

BOOL TMainDialog::TransmitLineMessage(LPLINE_DATA lpData)
{
    HEADER_DATA  toTransmit;
    
    toTransmit.message = kchLineMessage;
    if(m_CommunicationSocket.Send(&toTransmit, 
                                   sizeof(toTransmit)) != sizeof(toTransmit))
    {
        return(FALSE);
    }
    if(m_CommunicationSocket.Send(lpData, 
                                   sizeof(LINE_DATA)) != sizeof(LINE_DATA))
    {
        return(FALSE);
    }
    return(TRUE);
}  // TMainDialog::TransmitLineMessage

------------------------ receive code ------------------------
void TMainDialog::ReadSocketData()
{
    HEADER_DATA  toRead;
    
    if(m_CommunicationSocket.Receive(&toRead, 
                                           sizeof(toRead)) != sizeof(toRead))
    {
        // ... handle error ...
        return;
    }
    while(toRead.message != kchDoneMessage)
    {
        if(!ProcessMessage(toRead.message))
        {
            // ... handle error ...
            return;
        }
        if(m_CommunicationSocket.Receive(&toRead, 
                                            sizeof(toRead)) != sizeof(toRead))
        {
            // ... handle error ...
            return;
        }
    }
    // ... normal close ...
}  // TMainDialog::ReadSocketData

BOOL TMainDialog::ProcessMessage(char chMessage)
{
    BOOL  bConnectionOK = FALSE;
    switch(chMessage)
    {
        case(kchPixelMessage):
            bConnectionOK = ProcessPixelMessage();
            break;
        case(kchLineMessage):
            bConnectionOK = ProcessLineMessage();
            break;
    }
    return(bConnectionOK);
}  // TMainDialog::ProcessMessage

BOOL TMainDialog::ProcessPixelMessage()
{
    PIXEL_DATA  toRead;
    if(m_CommunicationSocket.Receive(&toRead,sizeof(toRead)) != sizeof(toRead))
    {
        return(FALSE);
    }
    // ... draw pixel ...
    return(TRUE);
}  // TMainDialog::ProcessPixelMessage

BOOL TMainDialog::ProcessLineMessage()
{
    LINE_DATA  toRead;
    if(m_CommunicationSocket.Receive(&toRead,sizeof(toRead)) != sizeof(toRead))
    {
        return(FALSE);
    // ... draw line ...
    return(TRUE);
}  // TMainDialog::ProcessLineMessage


Listing Two

void TMainDialog::ReadSocketData()
{
    HEADER_DATA  toRead;
    
    if(m_CommunicationSocket.Receive(&toRead,sizeof(toRead)) != sizeof(toRead))
    {
        // ... handle error ...
        return;
    }
    while(toRead.message != kchDoneMessage)
    {
        if(!ProcessMessage(toRead.message))
        {
            // ... handle error ...
            return;
        }
        if(m_CommunicationSocket.Receive(&toRead,
                                           sizeof(toRead)) != sizeof(toRead))
        {
            // ... handle error ...
            return;
        }
    }
    // ... normal close ...
}  // TMainDialog::ReadSocketData

BOOL TMainDialog::ProcessMessage(char chMessage)
{
    BOOL  bConnectionOK = FALSE;
    switch(chMessage)
    {
        case(kchPixelMessage):
            bConnectionOK = ProcessPixelMessage();
            break;
        case(kchLineMessage):
            bConnectionOK = ProcessLineMessage();
            break;
    }
    return(bConnectionOK);
}  // TMainDialog::ProcessMessage

BOOL TMainDialog::ProcessPixelMessage()
{
    PIXEL_DATA  toRead;
    
    if(m_CommunicationSocket.Receive(&toRead,sizeof(toRead)) != sizeof(toRead))
    {
        return(FALSE);
    }
    // ... draw pixel ...
    return(TRUE);
}  // TMainDialog::ProcessPixelMessage

BOOL TMainDialog::ProcessLineMessage()
{
    LINE_DATA  toRead;
    
    if(m_CommunicationSocket.Receive(&toRead,sizeof(toRead)) != sizeof(toRead))
    {
        return(FALSE);
    }
    // ... draw line ...
    return(TRUE);
}  // TMainDialog::ProcessLineMessage


Example 1:

char i;
Recv(s, &i, sizeof(char), NULL);
if (i != '0')
{
    ErrorHandler();
}
else
{
    ComputeResult(i);
}