NAME

       CURLMOPT_SOCKETFUNCTION - callback informed about what to wait for

SYNOPSIS

       #include <curl/curl.h>

       int socket_callback(CURL *easy,      /* easy handle */
                           curl_socket_t s, /* socket */
                           int what,        /* describes the socket */
                           void *userp,     /* private callback pointer */
                           void *socketp);  /* private socket pointer */

       CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETFUNCTION, socket_callback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above.

       When  the  curl_multi_socket_action(3)  function  runs,  it  informs the application about updates in the
       socket (file descriptor) status by doing none,  one,  or  multiple  calls  to  the  socket_callback.  The
       callback  gets status updates with changes since the previous time the callback was called.  If the given
       callback pointer  is  NULL,  no  callback  will  be  called.  Set  the  callback's  userp  argument  with
       CURLMOPT_SOCKETDATA(3).  See curl_multi_socket_action(3) for more details on how the callback is used and
       should work.

       The  what  parameter  informs  the  callback  on the status of the given socket. It can hold one of these
       values:

       CURL_POLL_IN
              Wait for incoming data. For the socket to become readable.

       CURL_POLL_OUT
              Wait for outgoing data. For the socket to become writable.

       CURL_POLL_INOUT
              Wait for incoming and outgoing data. For the socket to become readable or writable.

       CURL_POLL_REMOVE
              The specified socket/file descriptor is no longer used by libcurl.

DEFAULT

       NULL (no callback)

PROTOCOLS

       All

EXAMPLE

       static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
       {
         GlobalInfo *g = (GlobalInfo*) cbp;
         SockInfo *fdp = (SockInfo*) sockp;

         if(what == CURL_POLL_REMOVE) {
           remsock(fdp);
         }
         else {
           if(!fdp) {
             addsock(s, e, what, g);
           }
           else {
             setsock(fdp, s, e, what, g);
           }
         }
         return 0;
       }

       main()
       {
         GlobalInfo setup;
         /* ... use socket callback and custom pointer */
         curl_multi_setopt(multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
         curl_multi_setopt(multi, CURLMOPT_SOCKETDATA, &setup);
       }

AVAILABILITY

       Added in 7.15.4

RETURN VALUE

       Returns CURLM_OK.

SEE ALSO

       CURLMOPT_SOCKETDATA(3), curl_multi_socket_action(3), CURLMOPT_TIMERFUNCTION(3)

libcurl 7.58.0                                    May 31, 2017                        CURLMOPT_SOCKETFUNCTION(3)