curl / libcurl / API / curl_easy_setopt / CURLOPT_OPENSOCKETDATA

CURLOPT_OPENSOCKETDATA explained

Name

CURLOPT_OPENSOCKETDATA - pointer passed to open socket callback

Synopsis

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

Description

Pass a pointer that is untouched by libcurl and passed as the first argument in the open socket callback set with CURLOPT_OPENSOCKETFUNCTION.

Default

NULL

Protocols

This functionality affects all supported protocols

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;
}
 
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    extern int sockfd; /* the already connected one */
 
    /* libcurl thinks 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 curl 7.17.1

Return value

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