CURLOPT_HTTPPROXYTUNNEL(3) Library Functions Manual CURLOPT_HTTPPROXYTUNNEL(3)
NAME
CURLOPT_HTTPPROXYTUNNEL - tunnel through HTTP proxy
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPPROXYTUNNEL, long tunnel);
DESCRIPTION
Set the tunnel parameter to 1L to make libcurl tunnel all operations
through the HTTP proxy (set with CURLOPT_PROXY(3)). There is a big dif-
ference between using a proxy and to tunnel through it.
Tunneling means that an HTTP CONNECT request is sent to the proxy, ask-
ing it to connect to a remote host on a specific port number and then
the traffic is just passed through the proxy. Proxies tend to white-list
specific port numbers it allows CONNECT requests to and often only port
80 and 443 are allowed.
To suppress proxy CONNECT response headers from user callbacks use CUR-
LOPT_SUPPRESS_CONNECT_HEADERS(3).
HTTP proxies can generally only speak HTTP (for obvious reasons), which
makes libcurl convert non-HTTP requests to HTTP when using an HTTP proxy
without this tunnel option set. For example, asking for an FTP URL and
specifying an HTTP proxy makes libcurl send an FTP URL in an HTTP GET
request to the proxy. By instead tunneling through the proxy, you avoid
that conversion (that rarely works through the proxy anyway).
DEFAULT
0
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/file.txt");
curl_easy_setopt(curl, CURLOPT_PROXY, "http://127.0.0.1:80");
curl_easy_setopt(curl, CURLOPT_HTTPPROXYTUNNEL, 1L);
curl_easy_perform(curl);
}
}
AVAILABILITY
Added in curl 7.3
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_PROXY(3), CURLOPT_PROXYPORT(3), CURLOPT_PROXYTYPE(3)
libcurl 2026-07-12 CURLOPT_HTTPPROXYTUNNEL(3)
Generated by dwww version 1.16 on Sat Oct 3 05:38:58 CEST 2026.