Re: proper way to close a socket?

Hector Santos <>
Thu, 18 Mar 2010 00:01:59 -0400
Ok, Bill,

What you need to do is do wait on the Connect() like so:

     if(!m_pClientSocket->Connect(m_toURL, m_toPort)) {
       int err = GetLastError();
       if (err == WSAEWOULDBLOCK) {
          if (!m_pClientSocket->WaitConnect(5)) {
             // WaitConnect Error, Show Error
             err = GetLastError();
       } else {
          // Connect Error, Show Error
          err = GetLastError();

The WaitConnect() and AsyncYield() functions are a member of your
socket subclass

BOOL CMyClientSocket::WaitConnect(int nTimeout)
    int nSleep = 100;
    int nCountDown = nTimeout*1000 / nSleep;
    DWORD t1 = GetTickCount();
    for (;;) {
       if (nCountDown <= 0) {
          return FALSE;
       fd_set efds; fd_set wfds;
       FD_ZERO(&efds); FD_ZERO(&wfds);
       FD_SET(m_hSocket, &efds);
       FD_SET(m_hSocket, &wfds);
       struct timeval tv;
       tv.tv_sec = 0;
       tv.tv_usec = nSleep*1000;
       int rc = select(0, NULL, &wfds, &efds, &tv);
       switch (rc) {
       case 0:
          // WE TIMED OUT!!
             /* show timeout in some CListBox
             CString s;
             s.Format("- wait %d | %d",nCountDown, GetTickCount()-t1);
             if (AsyncYield(100)) {
                return FALSE;
       case SOCKET_ERROR:
          if (GetLastError() != WSAEWOULDBLOCK) return FALSE;
          if (FD_ISSET(m_hSocket,&wfds)) {
             // WE CONNECTED!!
             return TRUE;
          if (FD_ISSET(m_hSocket,&efds)) {
             // WE FAILED
             return FALSE;
    return FALSE;

BOOL CMyClientSocket::AsyncYield(DWORD nDelay)
     DWORD nDone = (GetTickCount() + nDelay);
     while (nDone > GetTickCount()){
         MSG msg;
         while (::PeekMessage(&msg,NULL,0,0,PM_REMOVE)){
       if (m_cancel) {
          m_cancel = FALSE;
          return TRUE;
     return FALSE;

My previous message had more details about using the select() socket
function. The wait block will use select() which allows you to detect
read, write and error events. In this case, you need two events:

    write event - signals the connection is ready
    error event - something went wrong

That will do the trick for you.


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