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Updated: Wednesday, July 27, 2022
 
 

curl_multi_socket_action (3)

Name

curl_multi_socket_action - reads/writes available data given an action

Synopsis

#include <curl/curl.h>

CURLMcode curl_multi_socket_action(CURLM *multi_handle,
curl_socket_t sockfd,
int ev_bitmask,
int *running_handles);

Description

libcurl Manual                                     curl_multi_socket_action(3)



NAME
       curl_multi_socket_action - reads/writes available data given an action

SYNOPSIS
       #include <curl/curl.h>

       CURLMcode curl_multi_socket_action(CURLM *multi_handle,
                                          curl_socket_t sockfd,
                                          int ev_bitmask,
                                          int *running_handles);

DESCRIPTION
       When  the  application  has  detected  action  on  a  socket handled by
       libcurl, it should call  curl_multi_socket_action(3)  with  the  sockfd
       argument set to the socket with the action. When the events on a socket
       are known, they can be passed as an events bitmask ev_bitmask by  first
       setting  ev_bitmask to 0, and then adding using bitwise OR (|) any com-
       bination of events to be chosen from CURL_CSELECT_IN,  CURL_CSELECT_OUT
       or  CURL_CSELECT_ERR.  When  the events on a socket are unknown, pass 0
       instead, and libcurl will test the descriptor internally.  It  is  also
       permissible  to  pass  CURL_SOCKET_TIMEOUT  to  the sockfd parameter in
       order to initiate the whole process or when a timeout occurs.

       At return, running_handles points to the number of running easy handles
       within  the  multi handle. When this number reaches zero, all transfers
       are complete/done. When you call curl_multi_socket_action(3) on a  spe-
       cific  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) function informs the application about
       updates in the socket (file descriptor) status by doing none,  one,  or
       multiple  calls  to  the  socket  callback  function set with the CURL-
       MOPT_SOCKETFUNCTION(3) 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(3) 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  argument  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.

       When this function returns error, the state of all transfers are uncer-
       tain  and  they cannot be continued. curl_multi_socket_action(3) should
       not be called again on the same multi handle after an  error  has  been
       returned, unless first removing all the handles and adding new ones.

TYPICAL USAGE
       1. Create a multi handle

       2. Set the socket callback with CURLMOPT_SOCKETFUNCTION(3)

       3.  Set  the timeout callback with CURLMOPT_TIMERFUNCTION(3), 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. Call curl_multi_socket_action(..., CURL_SOCKET_TIMEOUT, 0, ...)   to
       kickstart everything. To get one or more callbacks called.

       7. Wait for activity on any of libcurl's sockets, use the timeout value
       your callback has been told.

       8, 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.

EXAMPLE
       /* the event-library gets told when there activity on the socket 'fd',
          which we translate to a call to curl_multi_socket_action() */
       int running;
       rc = curl_multi_socket_action(multi_handle, fd, EVENT,
                                     &running);

AVAILABILITY
       This function was added in libcurl 7.15.4, and is deemed  stable  since
       7.16.0.

RETURN VALUE
       CURLMcode  type,  general  libcurl  multi  interface  error  code.  See
       libcurl-errors(3)


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | web/curl         |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+

SEE ALSO
       curl_multi_cleanup(3),     curl_multi_init(3),     curl_multi_fdset(3),
       curl_multi_info_read(3), the hiperfifo.c example



NOTES
       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source       was       downloaded      from       https://curl.se/down-
       load/curl-7.83.1.tar.bz2.

       Further information about this software can be found on the open source
       community website at http://curl.haxx.se/.



libcurl 7.83.1                 December 09, 2021
                                                   curl_multi_socket_action(3)