CURLOPT_LOCALPORT - local port number to use for socket

Added in curl 7.15.2

0, disabled - use whatever the system thinks is fine

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.

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); } }

CURLOPT_LOCALPORT - local port number to use for socket

This functionality affects all supported protocols

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).

CURLINFO_LOCAL_PORT(3), CURLOPT_INTERFACE(3), CURLOPT_LOCALPORTRANGE(3) libcurl 2025-06-16 CURLOPT_LOCALPORT(3)

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