proper way to close a socket?

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From: Hector Santos on 18 Mar 2010 00:01

---

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();
m_pClientSocket->Close();
return;
}
} else {
// Connect Error, Show Error
err = GetLastError();
m_pClientSocket->Close();
return;
}
}

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 (;;) {
nCountDown--;
if (nCountDown <= 0) {
SetLastError(WSAETIMEDOUT);
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);
m_dlg->m_log.InsertString(0,s);
*/
if (AsyncYield(100)) {
SetLastError(WSAECONNABORTED);
return FALSE;
}
}
break;
case SOCKET_ERROR:
if (GetLastError() != WSAEWOULDBLOCK) return FALSE;
break;
default:
if (FD_ISSET(m_hSocket,&wfds)) {
// WE CONNECTED!!
SetLastError(0);
return TRUE;
}
if (FD_ISSET(m_hSocket,&efds)) {
// WE FAILED
SetLastError(WSAEHOSTUNREACH);
return FALSE;
}
break;
}
}
return FALSE;
}

BOOL CMyClientSocket::AsyncYield(DWORD nDelay)
{
DWORD nDone = (GetTickCount() + nDelay);
while (nDone > GetTickCount()){
Sleep(75);
MSG msg;
while (::PeekMessage(&msg,NULL,0,0,PM_REMOVE)){
::TranslateMessage(&msg);
::DispatchMessage(&msg);
}
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.

--
HLS

From: Hector Santos on 18 Mar 2010 00:43

---

When I added the yield, I threw out the nCountDown timeout
calculation. Change it to this:

BOOL CMyClientSocket::WaitConnect(int nTimeout)
{
int nSleep = 100;
DWORD tFinal = GetTickCount()+nTimeout*1000;
for (;;) {
if (GetTickCount() > tFinal) {
SetLastError(WSAETIMEDOUT);
return FALSE;
}
....
}

---

Hector Santos wrote:

> 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();
> m_pClientSocket->Close();
> return;
> }
> } else {
> // Connect Error, Show Error
> err = GetLastError();
> m_pClientSocket->Close();
> return;
> }
> }
>
> 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 (;;) {
> nCountDown--;
> if (nCountDown <= 0) {
> SetLastError(WSAETIMEDOUT);
> 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);
> m_dlg->m_log.InsertString(0,s);
> */
> if (AsyncYield(100)) {
> SetLastError(WSAECONNABORTED);
> return FALSE;
> }
> }
> break;
> case SOCKET_ERROR:
> if (GetLastError() != WSAEWOULDBLOCK) return FALSE;
> break;
> default:
> if (FD_ISSET(m_hSocket,&wfds)) {
> // WE CONNECTED!!
> SetLastError(0);
> return TRUE;
> }
> if (FD_ISSET(m_hSocket,&efds)) {
> // WE FAILED
> SetLastError(WSAEHOSTUNREACH);
> return FALSE;
> }
> break;
> }
> }
> return FALSE;
> }
>
> BOOL CMyClientSocket::AsyncYield(DWORD nDelay)
> {
> DWORD nDone = (GetTickCount() + nDelay);
> while (nDone > GetTickCount()){
> Sleep(75);
> MSG msg;
> while (::PeekMessage(&msg,NULL,0,0,PM_REMOVE)){
> ::TranslateMessage(&msg);
> ::DispatchMessage(&msg);
> }
> 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.
>



--
HLS

From: "Bill" don't want more on 18 Mar 2010 06:22

---

Hector,

I tried to study and understand your code. Am I right that you are basically
polling the socket until it either connects or the connection attempt times
out?

Is there an advantage to this over waiting for the OnConnect call to come
with either no error meaning conencted or an error meaning timeout?

Will the OnConnect call always always always come in?

It seems a shame that there is no way to abort a connection attempt until it
gives up and gives the timeout. I'm wondering where does the timeout call
come from? If I'm trying to connect to an IP address that doesn't exist,
then I'm guessing that it's the socket code in Windows of my own PC that is
giving me the timeout. If that's the case, I'm surprised that it can't
coordinate that with a deleted object or one where Close was already called.

I suppose I could do one more thing. If the user presses the button to close
the connection before it's connected, I can leave that socket undeleted to
wait for the OnConnect and then delete itself inside the OnConnect call. If
the user presses the button again to make a new connection, I can create a
new socket to handle that request, even if the abandoned one is still not
shut down.

Thanks,

Bill


"Hector Santos" <sant9442(a)nospam.gmail.com> wrote in message
news:O2M8cWlxKHA.5940(a)TK2MSFTNGP02.phx.gbl...
> When I added the yield, I threw out the nCountDown timeout calculation.
> Change it to this:
>
> BOOL CMyClientSocket::WaitConnect(int nTimeout)
> {
> int nSleep = 100;
> DWORD tFinal = GetTickCount()+nTimeout*1000;
> for (;;) {
> if (GetTickCount() > tFinal) {
> SetLastError(WSAETIMEDOUT);
> return FALSE;
> }
> ....
> }
>
> ---
>
> Hector Santos wrote:
>
>> 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();
>> m_pClientSocket->Close();
>> return;
>> }
>> } else {
>> // Connect Error, Show Error
>> err = GetLastError();
>> m_pClientSocket->Close();
>> return;
>> }
>> }
>>
>> 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 (;;) {
>> nCountDown--;
>> if (nCountDown <= 0) {
>> SetLastError(WSAETIMEDOUT);
>> 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);
>> m_dlg->m_log.InsertString(0,s);
>> */
>> if (AsyncYield(100)) {
>> SetLastError(WSAECONNABORTED);
>> return FALSE;
>> }
>> }
>> break;
>> case SOCKET_ERROR:
>> if (GetLastError() != WSAEWOULDBLOCK) return FALSE;
>> break;
>> default:
>> if (FD_ISSET(m_hSocket,&wfds)) {
>> // WE CONNECTED!!
>> SetLastError(0);
>> return TRUE;
>> }
>> if (FD_ISSET(m_hSocket,&efds)) {
>> // WE FAILED
>> SetLastError(WSAEHOSTUNREACH);
>> return FALSE;
>> }
>> break;
>> }
>> }
>> return FALSE;
>> }
>>
>> BOOL CMyClientSocket::AsyncYield(DWORD nDelay)
>> {
>> DWORD nDone = (GetTickCount() + nDelay);
>> while (nDone > GetTickCount()){
>> Sleep(75);
>> MSG msg;
>> while (::PeekMessage(&msg,NULL,0,0,PM_REMOVE)){
>> ::TranslateMessage(&msg);
>> ::DispatchMessage(&msg);
>> }
>> 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.
>>
>
>
>
> --
> HLS

From: Hector Santos on 18 Mar 2010 10:12

---

Bill wrote:

> Hector,
>
> I tried to study and understand your code. Am I right that you are basically
> polling the socket until it either connects or the connection attempt times
> out?


It is basically waiting on signals. You don't have to do this. You
can simply override the Close() method and replace it with this:

//virtual
void CMyClientSocket::Close()
{
if (m_hSocket != INVALID_SOCKET)
{
VERIFY(SOCKET_ERROR != closesocket(m_hSocket));
//CAsyncSocket::KillSocket(m_hSocket, this);
m_hSocket = INVALID_SOCKET;
}
}

Notice the commenting out the CAsyncSocket::KillSocket(). That allows
you to invalidate the handle and continue to get a callback.

Now you can CLICK abort and call:

m_pClientSocket->Close();


> Is there an advantage to this over waiting for the OnConnect call to come
> with either no error meaning conencted or an error meaning timeout?


It allows you to monitor it. You can have a progress bar, you can have
a countdown, etc, you can shorten the timeout to 5, 10 seconds, etc!

But when using a Close() override, you can set a timer instead.

> Will the OnConnect call always always always come in?


Based on what I see, yes, IFF the handlers are still active for the
m_hSocket and CWnd thread

> It seems a shame that there is no way to abort a connection attempt until it
> gives up and gives the timeout.


You can do the above.

> I'm wondering where does the timeout call come from?

Its default for the socket stack. I don't see off hand how to change
it other than emulate the behavior (countdown) and/or use ::select()
to detect it yourself.

There is nothing kludgy about this, this is par for the course if you
want this type of monitoring behavior.

> If I'm trying to connect to an IP address that doesn't exist,
> then I'm guessing that it's the socket code in Windows of my own PC that is
> giving me the timeout. If that's the case, I'm surprised that it can't
> coordinate that with a deleted object or one where Close was already called.


Not with delete, but with Close() override.


> I suppose I could do one more thing. If the user presses the button to close
> the connection before it's connected, I can leave that socket undeleted to
> wait for the OnConnect and then delete itself inside the OnConnect call. If
> the user presses the button again to make a new connection, I can create a
> new socket to handle that request, even if the abandoned one is still not
> shut down.


Personally, you should *never* delete *any* object until everything is
settled. You can also override the destructor and clean things up
yourself first.

--
HLS

>
> Thanks,
>
> Bill
>
>
> "Hector Santos" <sant9442(a)nospam.gmail.com> wrote in message
> news:O2M8cWlxKHA.5940(a)TK2MSFTNGP02.phx.gbl...
>> When I added the yield, I threw out the nCountDown timeout calculation.
>> Change it to this:
>>
>> BOOL CMyClientSocket::WaitConnect(int nTimeout)
>> {
>> int nSleep = 100;
>> DWORD tFinal = GetTickCount()+nTimeout*1000;
>> for (;;) {
>> if (GetTickCount() > tFinal) {
>> SetLastError(WSAETIMEDOUT);
>> return FALSE;
>> }
>> ....
>> }
>>
>> ---
>>
>> Hector Santos wrote:
>>
>>> 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();
>>> m_pClientSocket->Close();
>>> return;
>>> }
>>> } else {
>>> // Connect Error, Show Error
>>> err = GetLastError();
>>> m_pClientSocket->Close();
>>> return;
>>> }
>>> }
>>>
>>> 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 (;;) {
>>> nCountDown--;
>>> if (nCountDown <= 0) {
>>> SetLastError(WSAETIMEDOUT);
>>> 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);
>>> m_dlg->m_log.InsertString(0,s);
>>> */
>>> if (AsyncYield(100)) {
>>> SetLastError(WSAECONNABORTED);
>>> return FALSE;
>>> }
>>> }
>>> break;
>>> case SOCKET_ERROR:
>>> if (GetLastError() != WSAEWOULDBLOCK) return FALSE;
>>> break;
>>> default:
>>> if (FD_ISSET(m_hSocket,&wfds)) {
>>> // WE CONNECTED!!
>>> SetLastError(0);
>>> return TRUE;
>>> }
>>> if (FD_ISSET(m_hSocket,&efds)) {
>>> // WE FAILED
>>> SetLastError(WSAEHOSTUNREACH);
>>> return FALSE;
>>> }
>>> break;
>>> }
>>> }
>>> return FALSE;
>>> }
>>>
>>> BOOL CMyClientSocket::AsyncYield(DWORD nDelay)
>>> {
>>> DWORD nDone = (GetTickCount() + nDelay);
>>> while (nDone > GetTickCount()){
>>> Sleep(75);
>>> MSG msg;
>>> while (::PeekMessage(&msg,NULL,0,0,PM_REMOVE)){
>>> ::TranslateMessage(&msg);
>>> ::DispatchMessage(&msg);
>>> }
>>> 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.
>>>
>>
>>
>> --
>> HLS
>

From: Joseph M. Newcomer on 18 Mar 2010 13:53

---

According to the CAsyncSocket documentation, when OnConnect is called, either the
connection has occurred (and you can do the Accept) or there has been an error (check the
input parameter to OnConnect). If you do the Accept, it is supposed to work, and if it
doesn't, you will get an error, at which point you deal with the error in the appropriate
fashion for your application, and simply return from OnConnect; it is over.
joe

On Thu, 18 Mar 2010 18:22:21 +0800, "Bill" <<don't want more spam>> wrote:

>Hector,
>
>I tried to study and understand your code. Am I right that you are basically
>polling the socket until it either connects or the connection attempt times
>out?
>
>Is there an advantage to this over waiting for the OnConnect call to come
>with either no error meaning conencted or an error meaning timeout?
>
>Will the OnConnect call always always always come in?
>
>It seems a shame that there is no way to abort a connection attempt until it
>gives up and gives the timeout. I'm wondering where does the timeout call
>come from? If I'm trying to connect to an IP address that doesn't exist,
>then I'm guessing that it's the socket code in Windows of my own PC that is
>giving me the timeout. If that's the case, I'm surprised that it can't
>coordinate that with a deleted object or one where Close was already called.
>
>I suppose I could do one more thing. If the user presses the button to close
>the connection before it's connected, I can leave that socket undeleted to
>wait for the OnConnect and then delete itself inside the OnConnect call. If
>the user presses the button again to make a new connection, I can create a
>new socket to handle that request, even if the abandoned one is still not
>shut down.
>
>Thanks,
>
>Bill
>
>
>"Hector Santos" <sant9442(a)nospam.gmail.com> wrote in message
>news:O2M8cWlxKHA.5940(a)TK2MSFTNGP02.phx.gbl...
>> When I added the yield, I threw out the nCountDown timeout calculation.
>> Change it to this:
>>
>> BOOL CMyClientSocket::WaitConnect(int nTimeout)
>> {
>> int nSleep = 100;
>> DWORD tFinal = GetTickCount()+nTimeout*1000;
>> for (;;) {
>> if (GetTickCount() > tFinal) {
>> SetLastError(WSAETIMEDOUT);
>> return FALSE;
>> }
>> ....
>> }
>>
>> ---
>>
>> Hector Santos wrote:
>>
>>> 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();
>>> m_pClientSocket->Close();
>>> return;
>>> }
>>> } else {
>>> // Connect Error, Show Error
>>> err = GetLastError();
>>> m_pClientSocket->Close();
>>> return;
>>> }
>>> }
>>>
>>> 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 (;;) {
>>> nCountDown--;
>>> if (nCountDown <= 0) {
>>> SetLastError(WSAETIMEDOUT);
>>> 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);
>>> m_dlg->m_log.InsertString(0,s);
>>> */
>>> if (AsyncYield(100)) {
>>> SetLastError(WSAECONNABORTED);
>>> return FALSE;
>>> }
>>> }
>>> break;
>>> case SOCKET_ERROR:
>>> if (GetLastError() != WSAEWOULDBLOCK) return FALSE;
>>> break;
>>> default:
>>> if (FD_ISSET(m_hSocket,&wfds)) {
>>> // WE CONNECTED!!
>>> SetLastError(0);
>>> return TRUE;
>>> }
>>> if (FD_ISSET(m_hSocket,&efds)) {
>>> // WE FAILED
>>> SetLastError(WSAEHOSTUNREACH);
>>> return FALSE;
>>> }
>>> break;
>>> }
>>> }
>>> return FALSE;
>>> }
>>>
>>> BOOL CMyClientSocket::AsyncYield(DWORD nDelay)
>>> {
>>> DWORD nDone = (GetTickCount() + nDelay);
>>> while (nDone > GetTickCount()){
>>> Sleep(75);
>>> MSG msg;
>>> while (::PeekMessage(&msg,NULL,0,0,PM_REMOVE)){
>>> ::TranslateMessage(&msg);
>>> ::DispatchMessage(&msg);
>>> }
>>> 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.
>>>
>>
>>
>>
>> --
>> HLS
>
Joseph M. Newcomer [MVP]
email: newcomer(a)flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm

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