CURLOPT_LOCALPORTRANGE(3) Introduction to Library Functions

NAME

CURLOPT_LOCALPORTRANGE - number of additional local ports to try

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_LOCALPORTRANGE,
long range);

DESCRIPTION

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.

DEFAULT

1

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode result;
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);
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}

AVAILABILITY

Added in curl 7.15.2

RETURN VALUE

curl_easy_setopt(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

CURLOPT_INTERFACE(3), CURLOPT_LOCALPORT(3)

libcurl 2026-01-08 CURLOPT_LOCALPORTRANGE(3)