On Fri, 20 Mar 2009, Chad Monroe wrote:

> * Expire cleared
> * Connection #0 to host 10.4.4.204 left intact
>
> About ~10 seconds later the server sends another packet on this socket,
> poll() fires, and my application calls curl_multi_perform(). I'm guessing
> that because the transfer is finished, curl_multi_perform() does not perform
> any action on this socket as I get stuck in this loop forever. poll()
> continuously fires with an event of POLLIN and curl_multi_perform() gets
> called. curl_multi_fdset() still reports the descriptor as in use at this
> time.

I don't get it. If the transfer is complete and the socket is no longer used
by any active easy handle, why does it still get used in poll() ? The moment
that transfer was completed, libcurl will of course no longer use that socket
nor care about it if something arrives on it.

> Looking at the libcurl code, it looks like sockets are only closed upon
> error, or when calling curl_multi_cleanup().

Yes, or if the server says so or just closes it, or if you tell libcurl to not
re-use the handle for that specific transfer (CURLOPT_FORBID_REUSE).

> 1.) retrieve all sockets used by a specific easy handle so I can close them
> manually
> 2.) tell libcurl to close all sockets associated with an easy handle

Neither option exist but for the reason that they really shouldn't be needed.
You _either_ don't want the connection to be kept around and re-use and then
you tell libcurl to not re-use it, or you want it to be re-use and then you
want it kept open as much as possible (of course limited by the limiter for
max number of connections).

And recently libcurl has also got a lot better to kill connections that died
recently, even before they are attempted to get re-used so thus it will now
keep less sockets in TIME_WAIT or other "almost-dead" states.

> Or is there some other better way to solve my problem?

The primary question is simply why you poll() on sockets not used by libcurl
any longer?

-- 
  / daniel.haxx.se