CURLOPT_CLOSESOCKETDATA(3) Introduction to Library Functions

NAME

CURLOPT_CLOSESOCKETDATA - pointer passed to the socket close callback

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CLOSESOCKETDATA,
void *pointer);

DESCRIPTION

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

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_CLOSESOCKETFUNCTION(3), CURLOPT_OPENSOCKETFUNCTION(3)

libcurl 2026-01-08 CURLOPT_CLOSESOCKETDATA(3)