curl_multi_socket(3)
curl_multi_socket(3) libcurl Manual curl_multi_socket(3)
NAME
curl_multi_socket - reads/writes available data
SYNOPSIS
#include <curl/curl.h>
CURLMcode curl_multi_socket(CURLM * multi_handle, curl_socket_t sockfd,
int *running_handles);
CURLMcode curl_multi_socket_all(CURLM *multi_handle,
int *running_handles);
DESCRIPTION
These functions are deprecated. Do not use! See
curl_multi_socket_action(3) instead!
At return, the integer running_handles points to will con-
tain the number of still running easy handles within the
multi handle. When this number reaches zero, all transfers
are complete/done. Note that when you call
curl_multi_socket_action(3) on a specific socket and the
counter decreases by one, it DOES NOT necessarily mean that
this exact socket/transfer is the one that completed. Use
curl_multi_info_read(3) to figure out which easy handle that
completed.
The curl_multi_socket_action(3) functions inform the appli-
cation about updates in the socket (file descriptor) status
by doing none, one, or multiple calls to the socket callback
function set with the CURLMOPT_SOCKETFUNCTION option to
curl_multi_setopt(3). They update the status with changes
since the previous time the callback was called.
Get the timeout time by setting the CURLMOPT_TIMERFUNCTION
option with curl_multi_setopt(3). Your application will then
get called with information on how long to wait for socket
actions at most before doing the timeout action: call the
curl_multi_socket_action(3) function with the sockfd argu-
ment set to CURL_SOCKET_TIMEOUT. You can also use the
curl_multi_timeout(3) function to poll the value at any
given time, but for an event-based system using the callback
is far better than relying on polling the timeout value.
Usage of curl_multi_socket(3) is deprecated, whereas the
function is equivalent to curl_multi_socket_action(3) with
ev_bitmask set to 0.
Force libcurl to (re-)check all its internal sockets and
transfers instead of just a single one by calling
curl_multi_socket_all(3). Note that there should not be any
reason to use this function!
libcurl 7.58.0 Last change: December 15, 2016 1
curl_multi_socket(3) libcurl Manual curl_multi_socket(3)
CALLBACK DETAILS
The socket callback function uses a prototype like this
int curl_socket_callback(CURL *easy, /* easy handle */
curl_socket_t s, /* socket */
int action, /* see values below */
void *userp, /* private callback pointer */
void *socketp); /* private socket pointer */
The callback MUST return 0.
The easy argument is a pointer to the easy handle that deals
with this particular socket. Note that a single handle may
work with several sockets simultaneously.
The s argument is the actual socket value as you use it
within your system.
The action argument to the callback has one of five values:
CURL_POLL_NONE (0)
register, not interested in readiness (yet)
CURL_POLL_IN (1)
register, interested in read readiness
CURL_POLL_OUT (2)
register, interested in write readiness
CURL_POLL_INOUT (3)
register, interested in both read and write readi-
ness
CURL_POLL_REMOVE (4)
unregister
The socketp argument is a private pointer you have previ-
ously set with curl_multi_assign(3) to be associated with
the s socket. If no pointer has been set, socketp will be
NULL. This argument is of course a service to applications
that want to keep certain data or structs that are strictly
associated to the given socket.
The userp argument is a private pointer you have previously
set with curl_multi_setopt(3) and the CURLMOPT_SOCKETDATA
option.
RETURN VALUE
CURLMcode type, general libcurl multi interface error code.
Legacy: If you receive CURLM_CALL_MULTI_PERFORM, this basi-
cally means that you should call curl_multi_socket(3) again,
libcurl 7.58.0 Last change: December 15, 2016 2
curl_multi_socket(3) libcurl Manual curl_multi_socket(3)
before you wait for more actions on libcurl's sockets. You
don't have to do it immediately, but the return code means
that libcurl may have more data available to return or that
there may be more data to send off before it is "satisfied".
In modern libcurls, CURLM_CALL_MULTI_PERFORM or
CURLM_CALL_MULTI_SOCKET should not be returned and no appli-
cation needs to care about them.
NOTE that the return code is for the whole multi stack.
Problems still might have occurred on individual transfers
even when one of these functions return OK.
TYPICAL USAGE
1. Create a multi handle
2. Set the socket callback with CURLMOPT_SOCKETFUNCTION
3. Set the timeout callback with CURLMOPT_TIMERFUNCTION, to
get to know what timeout value to use when waiting for
socket activities.
4. Add easy handles with curl_multi_add_handle()
5. Provide some means to manage the sockets libcurl is
using, so you can check them for activity. This can be done
through your application code, or by way of an external
library such as libevent or glib.
6. Wait for activity on any of libcurl's sockets, use the
timeout value your callback has been told
7, When activity is detected, call
curl_multi_socket_action() for the socket(s) that got
action. If no activity is detected and the timeout expires,
call curl_multi_socket_action(3) with CURL_SOCKET_TIMEOUT
8. Go back to step 6.
AVAILABILITY
This function was added in libcurl 7.15.4, and is deemed
stable since 7.16.0.
curl_multi_socket(3) is deprecated, use
curl_multi_socket_action(3) instead!
SEE ALSO
curl_multi_cleanup(3), curl_multi_init(3),
curl_multi_fdset(3), curl_multi_info_read(3), the
hiperfifo.c example
libcurl 7.58.0 Last change: December 15, 2016 3
Man(1) output converted with
man2html