CURLINFO_CONN_ID - get the ID of the last connection used by the handle

#include <curl/curl.h>
CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CONN_ID,
                           curl_off_t *conn_id);

Pass a pointer to a curl_off_t to receive the connection identifier last used by the handle. Stores -1 if there was no connection used.

The connection id is unique among all connections using the same connection cache. This is implicitly the case for all connections in the same multi handle.


CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_URL, "");
  /* Perform the request */
  res = curl_easy_perform(curl);
  if(!res) {
    curl_off_t conn_id;
    res = curl_easy_getinfo(curl, CURLINFO_CONN_ID, &conn_id);
    if(!res) {
      printf("Connection used: %" CURL_FORMAT_CURL_OFF_T "\n", conn_id);

Added in 8.2.0

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

curl_easy_getinfo(3), curl_easy_setopt(3), CURLINFO_XFER_ID(3)

September 26, 2023 libcurl 8.4.0