curl/docs/examples/localport.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/
/* <DESC>
 * Use CURLOPT_LOCALPORT to control local port number
 * </DESC>
 */
#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
  CURL *curl;
  CURLcode res = CURLE_OK;

  curl = curl_easy_init();
  if(curl) {
    /* Try to use a local port number between 20000-20009 */
    curl_easy_setopt(curl, CURLOPT_LOCALPORT, 20000L);
    /* 10 means number of attempts, which starts with the number set in
       CURLOPT_LOCALPORT. The lower value set, the smaller the chance it
       works. */
    curl_easy_setopt(curl, CURLOPT_LOCALPORTRANGE, 10L);
    curl_easy_setopt(curl, CURLOPT_URL, "https://curl.se/");

    res = curl_easy_perform(curl);

    /* always cleanup */
    curl_easy_cleanup(curl);
  }

  return (int)res;
}