NAME

       CURLOPT_CLOSESOCKETFUNCTION - callback to socket close replacement

SYNOPSIS

       #include <curl/curl.h>

       int closesocket_callback(void *clientp, curl_socket_t item);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CLOSESOCKETFUNCTION,
                                 closesocket_callback);

DESCRIPTION

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

       This callback function gets called by libcurl instead of the close(3) or closesocket(3) call when sockets
       are   closed   (not   for  any  other  file  descriptors).  This  is  pretty  much  the  reverse  to  the
       CURLOPT_OPENSOCKETFUNCTION(3) option. Return 0 to signal success and 1 if there was an error.

       The clientp pointer is set with CURLOPT_CLOSESOCKETDATA(3). item  is  the  socket  libcurl  wants  to  be
       closed.

       Note  that  when  using multi/share handles, your callback may get invoked even after the easy handle has
       been cleaned up. The callback and data is inherited by a new connection  and  that  connection  may  live
       longer than the transfer itself in the multi/share handle's connection cache.

DEFAULT

       Use the standard socket close function.

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       struct priv {
         void *custom;
       };

       static int closesocket(void *clientp, curl_socket_t item)
       {
         struct priv *my = clientp;
         printf("our ptr: %p\n", my->custom);

         printf("libcurl wants to close %d now\n", (int)item);
         return 0;
       }

       int main(void)
       {
         struct priv myown;
         CURL *curl = curl_easy_init();

         /* call this function to close sockets */
         curl_easy_setopt(curl, CURLOPT_CLOSESOCKETFUNCTION, closesocket);
         curl_easy_setopt(curl, CURLOPT_CLOSESOCKETDATA, &myown);

         curl_easy_perform(curl);
         curl_easy_cleanup(curl);
       }

AVAILABILITY

       Added in curl 7.21.7

RETURN VALUE

       curl_easy_setopt(3) returns a CURLcode indicating success or error.

       CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

SEE ALSO

       CURLOPT_CLOSESOCKETDATA(3), CURLOPT_OPENSOCKETFUNCTION(3)

libcurl                                            2025-11-07                     CURLOPT_CLOSESOCKETFUNCTION(3)