DOKK / manpages / debian 12 / libcurl4-doc / CURLOPT_LOCALPORT.3.en
CURLOPT_LOCALPORT(3) curl_easy_setopt options CURLOPT_LOCALPORT(3)

CURLOPT_LOCALPORT - local port number to use for socket

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

Pass a long. This sets the local port number of the socket used for the connection. This can be used in combination with CURLOPT_INTERFACE(3) and you are recommended to use CURLOPT_LOCALPORTRANGE(3) as well when this option is set. Valid port numbers are 1 - 65535.

0, disabled - use whatever the system thinks is fine

All

CURL *curl = curl_easy_init();
if(curl) {

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);
ret = curl_easy_perform(curl);
curl_easy_cleanup(curl); }

Added in 7.15.2

Returns CURLE_OK

CURLOPT_LOCALPORTRANGE(3), CURLOPT_INTERFACE(3),

January 2, 2023 libcurl 7.88.1