---
name: "CURLOPT_SOCKOPTDATA"
section: "3"
platform: "macos"
package: "curl"
version: "166.0.0.0.1"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_SOCKOPTDATA"
---

# CURLOPT\_SOCKOPTDATA(3)

pointer to pass to sockopt callback

## NAME

CURLOPT\_SOCKOPTDATA - pointer to pass to sockopt callback

## SYNOPSIS

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

## DESCRIPTION

Pass a *pointer* that is untouched by libcurl and passed as the first argument in the sockopt callback set with *[CURLOPT\_SOCKOPTFUNCTION(3)](/CURLOPT_SOCKOPTFUNCTION/3.md)*.

## DEFAULT

The default value of this parameter is NULL.

## PROTOCOLS

All

## EXAMPLE

```
static int sockopt_callback(void *clientp, curl_socket_t curlfd,
                            curlsocktype purpose)
{
  int val = *(int *)clientp;
  setsockopt((int)curlfd, SOL_SOCKET, SO_RCVBUF,
             (const char *)&val, sizeof(val));
  return CURL_SOCKOPT_OK;
}
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    int recvbuffersize = 256 * 1024;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    /* call this function to set options for the socket */
    curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
    curl_easy_setopt(curl, CURLOPT_SOCKOPTDATA, &recvbuffersize);
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in 7.16.0

## RETURN VALUE

Returns *CURLE\_OK* if the option is supported, and *CURLE\_UNKNOWN\_OPTION* if not.

## SEE ALSO

[**CURLOPT\_OPENSOCKETFUNCTION**(3)](/CURLOPT_OPENSOCKETFUNCTION/3.md), [**CURLOPT\_SOCKOPTFUNCTION**(3)](/CURLOPT_SOCKOPTFUNCTION/3.md)