curl / libcurl / API / curl_easy_setopt / CURLOPT_CLOSESOCKETFUNCTION

CURLOPT_CLOSESOCKETFUNCTION explained

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 option. Return 0 to signal success and 1 if there was an error.

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

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

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.