CURLINFO_LASTSOCKET - get the last socket used

#include <curl/curl.h>
CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_LASTSOCKET, long *socket);

Deprecated since 7.45.0. Use CURLINFO_ACTIVESOCKET(3) instead.

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 If the socket is no longer valid, -1 is returned.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(3) 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.


int main(void)
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    long sockfd; /* does not work on win64! */
    curl_easy_setopt(curl, CURLOPT_URL, "");
    /* Do not do the transfer - only connect to host */
    curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
    res = curl_easy_perform(curl);
    if(res != CURLE_OK) {
      printf("Error: %s\n", curl_easy_strerror(res));
      return 1;
    /* Extract the socket from the curl handle */
    res = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockfd);
    if(!res && sockfd != -1) {
      /* operate on sockfd */

Added in 7.15.2

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

CURLINFO_ACTIVESOCKET(3), CURLOPT_CONNECT_ONLY(3), curl_easy_getinfo(3), curl_easy_setopt(3)

2024-05-22 libcurl