CURLOPT_OPENSOCKETDATA

Section: curl_easy_setopt options (3)
Updated: November 04, 2020
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NAME

CURLOPT_OPENSOCKETDATA - custom pointer passed to open socket callback

SYNOPSIS

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

DESCRIPTION

Pass a pointer that will be untouched by libcurl and passed as the first argument in the opensocket callback set with CURLOPT_OPENSOCKETFUNCTION(3).

DEFAULT

The default value of this parameter is NULL.

PROTOCOLS

All

EXAMPLE

/* make libcurl use the already established socket 'sockfd' */

static curl_socket_t opensocket(void *clientp,
                                curlsocktype purpose,
                                struct curl_sockaddr *address)
{
  curl_socket_t sockfd;
  sockfd = *(curl_socket_t *)clientp;
  /* the actual externally set socket is passed in via the OPENSOCKETDATA
     option */
  return sockfd;
}

static int sockopt_callback(void *clientp, curl_socket_t curlfd,
                            curlsocktype purpose)
{
  /* This return code was added in libcurl 7.21.5 */
  return CURL_SOCKOPT_ALREADY_CONNECTED;
}

curl = curl_easy_init();
if(curl) {
  /* libcurl will internally think that you connect to the host
   * and port that you specify in the URL option. */
  curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
  /* call this function to get a socket */
  curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
  curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);

  /* call this function to set options for the socket */
  curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);

  res = curl_easy_perform(curl);

  curl_easy_cleanup(curl);
}

AVAILABILITY

Added in 7.17.1

RETURN VALUE

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.