On Mar 21, 2009, at 9:25 AM, Daniel Stenberg wrote:

> 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

Hi Daniel,

Thanks for the quick response. The reason I continue to poll() on
sockets "not used by libcurl any longer" is because curl_multi_fdset()
returns them in the fd_set data even after the connection has
finished. I assume this is because libcurl leaves the sockets open as
denoted by the message:

* Connection #0 to host 10.4.4.204 left intact

I'm not sure if this is the intended behavior of curl_multi_fdset() or
if it's possibly a bug. If you think it's an issue I can investigate
further if you'd like.

In any case, I checked out CURLOPT_FORBID_REUSE and it causes libcurl
to perform exactly how I want. When the connection is complete it
closes the sockets and removes them from the fd_set returned by
curl_multi_fdset() which causes my application to remove them from
poll().

--
Chad Monroe