CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_LASTSOCKET, long *socket);
Pass a pointer to a long to receive the last socket used by this curl session. If the socket is no longer valid, -1 is returned. When you finish working with the socket, you must call curl_easy_cleanup() as usual and let libcurl close the socket and cleanup other resources associated with the handle. This is typically used in combination with CURLOPT_CONNECT_ONLY(3).
NOTE: this API is deprecated since it is not working on win64 where the SOCKET type is 64 bits large while its 'long' is 32 bits. Use the CURLINFO_ACTIVESOCKET(3) instead, if possible.
CURL *curl = curl_easy_init();
if(curl) {
long sockfd; /* doesn't work on win64! */
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
/* Do not do the transfer - only connect to host */
curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
res = curl_easy_perform(curl);
/* Extract the socket from the curl handle */
res = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockfd);
if(res != CURLE_OK) {
printf("Error: %s\n", curl_easy_strerror(res));
return 1;
}
}