.\" generated by cd2nroff 0.1 from CURLOPT_CLOSESOCKETFUNCTION.md
.TH CURLOPT_CLOSESOCKETFUNCTION 3 "2025-10-19" libcurl
.SH NAME
CURLOPT_CLOSESOCKETFUNCTION \- callback to socket close replacement
.SH SYNOPSIS
.nf
#include <curl/curl.h>

int closesocket_callback(void *clientp, curl_socket_t item);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CLOSESOCKETFUNCTION,
                          closesocket_callback);
.fi
.SH 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 \fIclose(3)\fP or
\fIclosesocket(3)\fP call when sockets are closed (not for any other file
descriptors). This is pretty much the reverse to the
\fICURLOPT_OPENSOCKETFUNCTION(3)\fP option. Return 0 to signal success and 1
if there was an error.

The \fIclientp\fP pointer is set with
\fICURLOPT_CLOSESOCKETDATA(3)\fP. \fIitem\fP 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\(aqs connection cache.
.SH DEFAULT
Use the standard socket close function.
.SH PROTOCOLS
This functionality affects all supported protocols
.SH EXAMPLE
.nf
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);
}
.fi
.SH AVAILABILITY
Added in curl 7.21.7
.SH RETURN VALUE
\fIcurl_easy_setopt(3)\fP returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non\-zero means an error occurred, see
\fIlibcurl\-errors(3)\fP.
.SH SEE ALSO
.BR CURLOPT_CLOSESOCKETDATA (3),
.BR CURLOPT_OPENSOCKETFUNCTION (3)