CURLOPT_LOCALPORTRANGE(3) Library Functions Manual CURLOPT_LOCALPORTRANGE(3)

CURLOPT_LOCALPORTRANGE - number of additional local ports to try

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_LOCALPORTRANGE,
                          long range);

Pass a long. The range argument is the number of attempts libcurl makes to find a working local port number. It starts with the given CURLOPT_LOCALPORT(3) and adds one to the number for each retry. Setting this option to 1 or below makes libcurl only do one try for the exact port number. Port numbers by nature are scarce resources that are busy at times so setting this value to something too low might cause unnecessary connection setup failures.

1

All

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
    curl_easy_setopt(curl, CURLOPT_LOCALPORT, 49152L);
    /* and try 20 more ports following that */
    curl_easy_setopt(curl, CURLOPT_LOCALPORTRANGE, 20L);
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

Added in 7.15.2

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

CURLOPT_INTERFACE(3), CURLOPT_LOCALPORT(3)

2024-05-22 libcurl