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)