curl-w32/docs/libcurl/opts/CURLOPT_OPENSOCKETDATA.md

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---
c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_OPENSOCKETDATA
Section: 3
Source: libcurl
See-also:
- CURLOPT_CLOSESOCKETFUNCTION (3)
- CURLOPT_OPENSOCKETFUNCTION (3)
- CURLOPT_SOCKOPTFUNCTION (3)
---
# NAME
CURLOPT_OPENSOCKETDATA - pointer passed to open socket callback
# SYNOPSIS
~~~c
#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
The default value of this parameter is NULL.
# PROTOCOLS
All
# EXAMPLE
~~~c
/* 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 7.17.1
# RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.