CURLOPT_LOCALPORT(3) Library Functions Manual CURLOPT_LOCALPORT(3)
NAME
CURLOPT_LOCALPORT - local port number to use for socket
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_LOCALPORT, long port);
DESCRIPTION
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.
DEFAULT
0, disabled - use whatever the system thinks is fine
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
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);
}
}
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
CURLINFO_LOCAL_PORT(3), CURLOPT_INTERFACE(3), CURLOPT_LOCALPORTRANGE(3)
libcurl 2026-07-12 CURLOPT_LOCALPORT(3)
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