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                     23: .TH CURLOPT_HTTPPROXYTUNNEL 3 "March 23, 2020" "libcurl 7.70.0" "curl_easy_setopt options"
                     24: 
                     25: .SH NAME
                     26: CURLOPT_HTTPPROXYTUNNEL \- tunnel through HTTP proxy
                     27: .SH SYNOPSIS
                     28: #include <curl/curl.h>
                     29: 
                     30: CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPPROXYTUNNEL, long tunnel);
                     31: .SH DESCRIPTION
                     32: Set the \fBtunnel\fP parameter to 1L to make libcurl tunnel all operations
                     33: through the HTTP proxy (set with \fICURLOPT_PROXY(3)\fP). There is a big
                     34: difference between using a proxy and to tunnel through it.
                     35: 
                     36: Tunneling means that an HTTP CONNECT request is sent to the proxy, asking it
                     37: to connect to a remote host on a specific port number and then the traffic is
                     38: just passed through the proxy. Proxies tend to white-list specific port numbers
                     39: it allows CONNECT requests to and often only port 80 and 443 are allowed.
                     40: 
                     41: To suppress proxy CONNECT response headers from user callbacks use
                     42: \fICURLOPT_SUPPRESS_CONNECT_HEADERS(3)\fP.
                     43: 
                     44: HTTP proxies can generally only speak HTTP (for obvious reasons), which makes
                     45: libcurl convert non-HTTP requests to HTTP when using an HTTP proxy without
                     46: this tunnel option set. For example, asking for an FTP URL and specifying an
                     47: HTTP proxy will make libcurl send an FTP URL in an HTTP GET request to the
                     48: proxy. By instead tunneling through the proxy, you avoid that conversion (that
                     49: rarely works through the proxy anyway).
                     50: .SH DEFAULT
                     51: 0
                     52: .SH PROTOCOLS
                     53: All network protocols
                     54: .SH EXAMPLE
                     55: .nf
                     56: CURL *curl = curl_easy_init();
                     57: if(curl) {
                     58:   curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/file.txt");
                     59:   curl_easy_setopt(curl, CURLOPT_PROXY, "http://127.0.0.1:80");
                     60:   curl_easy_setopt(curl, CURLOPT_HTTPPROXYTUNNEL, 1L);
                     61:   curl_easy_perform(curl);
                     62: }
                     63: .fi
                     64: .SH AVAILABILITY
                     65: Always
                     66: .SH RETURN VALUE
                     67: Returns CURLE_OK
                     68: .SH "SEE ALSO"
                     69: .BR CURLOPT_PROXY "(3), " CURLOPT_PROXYTYPE "(3), " CURLOPT_PROXYPORT "(3), "