CURLOPT\_CLOSESOCKETDATA(3) Library Functions Manual CURLOPT\_CLOSESOCKETDATA(3)

# [NAME](#NAME)

CURLOPT\_CLOSESOCKETDATA - pointer passed to the socket close callback

# [SYNOPSIS](#SYNOPSIS)

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CLOSESOCKETDATA,


                          void *pointer);
```

# [DESCRIPTION](#DESCRIPTION)

Pass a *pointer* that remains untouched by libcurl and passed as the first argument in the closesocket callback set with [*CURLOPT\_CLOSESOCKETFUNCTION(3)*](/man/os/curl/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](#DEFAULT)

NULL

# [PROTOCOLS](#PROTOCOLS)

This functionality affects all supported protocols

# [EXAMPLE](#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();


  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);


  }
}
```

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.21.7

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/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)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

[**CURLOPT\_CLOSESOCKETFUNCTION**(3)](/man/os/curl/CURLOPT_CLOSESOCKETFUNCTION.3), [**CURLOPT\_OPENSOCKETFUNCTION**(3)](/man/os/curl/CURLOPT_OPENSOCKETFUNCTION.3)

2026-09-24 libcurl

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Document: CURLOPT_CLOSESOCKETDATA(3) from curl 8.22.0-r3 (Chainguard OS)
Source: https://github.com/curl/curl.git