CURLINFO_LASTSOCKET(3)

💅 CURLINFO_LASTSOCKET(3) — last socket used

okay so this is the Library Functions Manual page for CURLINFO_LASTSOCKET(3), and it is lowkey all about the last socket used. bestie, let's get into it 🫶

✨ NAME ✨

CURLINFO_LASTSOCKET — last socket used 💫

🌸 SYNOPSIS 🌸

#include <curl/curl.h>

CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_LASTSOCKET, long *socket);

🦋 DESCRIPTION 🦋

Okay so first things first: Deprecated since 7.45.0. Use CURLINFO_ACTIVESOCKET(3) instead, bestie. no cap 💀

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 If the socket is no longer valid, -1 is returned.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. 😭

🌈 PROTOCOLS 🌈

This functionality affects all supported protocols 🌐✨

🍓 EXAMPLE 🍓

Here is the example, bestie, looking iconic and staying exactly as it should:

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    long sockfd; /* does not 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);
    result = curl_easy_perform(curl);
    if(result != CURLE_OK) {
      printf("Error: %s\n", curl_easy_strerror(result));
      curl_easy_cleanup(curl);
      return 1;
    }

    /* Extract the socket from the curl handle */
    result = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockfd);
    if(!result && sockfd != -1) {
      /* operate on sockfd */
    }

    curl_easy_cleanup(curl);
  }
}

🎀 AVAILABILITY 🎀

Added in curl 7.15.2 👑 periodt.

💜 RETURN VALUE 💜

curl_easy_getinfo(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). 🫶

🔥 SEE ALSO 🔥

• CURLINFO_ACTIVESOCKET(3)
• CURLOPT_CONNECT_ONLY(3)
• curl_easy_getinfo(3)
• curl_easy_setopt(3)

xoxo, libcurl • 2026-10-12 • CURLINFO_LASTSOCKET(3) — stay socket-y, bestie 💖