Re: proper way to close a socket?

From:
Stephen Myers <""StephenMyers\"@discussions@microsoft.com">
Newsgroups:
microsoft.public.vc.mfc
Date:
Wed, 10 Mar 2010 08:01:08 -0600
Message-ID:
<us7qjoFwKHA.4492@TK2MSFTNGP05.phx.gbl>
Bill Brehm wrote:

I have a problem with CAsynsocket. I can connect to a remote socket. When I
want to close the connection, I just delete the socket object (which closes
the connection) and have no problems.

But if I've started to connect to a remote socket that doesn't exist (or
doesn't accept), and I delete the local socket object while waiting for the
connection, I sometimes get an assert in CAsyncSocket::DoCallBack(). See
below. Actually, it's not in the middle of an Accept call because I test
with an address and port that I know doesn't exist.

Any idea how I should be doing this so as not to crash my program?

Thanks,

Bill

void PASCAL CAsyncSocket::DoCallBack(WPARAM wParam, LPARAM lParam)
{
 if (wParam == 0 && lParam == 0)
  return;

 // Has the socket be closed?
 CAsyncSocket* pSocket = CAsyncSocket::LookupHandle((SOCKET)wParam, TRUE);

 // If yes ignore message
 if (pSocket != NULL)
  return;

 pSocket = CAsyncSocket::LookupHandle((SOCKET)wParam, FALSE);
 if (pSocket == NULL)
 {
  // Must be in the middle of an Accept call
  pSocket = CAsyncSocket::LookupHandle(INVALID_SOCKET, FALSE);
  ASSERT(pSocket != NULL);
<-------------------------------------------------asserts here sometimes but
not always.
  pSocket->m_hSocket = (SOCKET)wParam;
  CAsyncSocket::DetachHandle(INVALID_SOCKET, FALSE);
  CAsyncSocket::AttachHandle(pSocket->m_hSocket, pSocket, FALSE);
 }


My guess is that the Connect handling is causing the problem. Connect()
will return immediately. You will then get OnConnect(), with or without
an error. The timeout varies, but I would expect it to be on the order
of 5 seconds. Once OnConnect has been called you should be able to
close the socket.

HTH
Steve

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