CURLOPT_CLOSESOCKETDATA(3)

CURLOPT_CLOSESOCKETDATA3

Pointer passed to the socket close callback

Usage

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CLOSESOCKETDATA,
                          void *pointer);

Overview

Pass a pointer that remains untouched by libcurl and passed as the first argument in the closesocket callback set with CURLOPT_CLOSESOCKETFUNCTION(3).

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

NULL

Protocols

This functionality affects all supported protocols

Examples

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();
  if(curl) {
    CURLcode result;
    /* call this function to close sockets */
    curl_easy_setopt(curl, CURLOPT_CLOSESOCKETFUNCTION, closesocket);
    curl_easy_setopt(curl, CURLOPT_CLOSESOCKETDATA, &myown);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

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).

Releases

7 releases since Debian 8 (Jessie); the text changed 6 times.

  1. 8
  2. 9
  3. 10
  4. 11
  5. 12
  6. 13
  7. Arch

Availability

Added in curl 7.21.7

From curl 8.23.0-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.