Tribblix: manual page: CURLOPT

CURLOPT_OPENSOCKETDATA(3) Introduction to Library Functions

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(3).

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

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).