CURLMOPT_SOCKETFUNCTION − callback informed about what to wait for
int socket_callback(CURL *easy, /* easy handle */
curl_socket_t s, /* socket */
int what, /* see above */
void *userp, /* private callback pointer */
void *socketp); /* private socket pointer */
CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETFUNCTION, socket_callback);
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.
NULL (no callback)
Added in 7.15.4
CURLMOPT_SOCKETDATA(3), curl_multi_socket_action(3), CURLMOPT_TIMERFUNCTION(3)