DOKK / manpages / debian 10 / libcurl4-doc / CURLOPT_FTP_SSL_CCC.3.en
CURLOPT_FTP_SSL_CCC(3) curl_easy_setopt options CURLOPT_FTP_SSL_CCC(3)

CURLOPT_FTP_SSL_CCC - switch off SSL again with FTP after auth

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_FTP_SSL_CCC,
long how);

If enabled, this option makes libcurl use CCC (Clear Command Channel). It shuts down the SSL/TLS layer after authenticating. The rest of the control channel communication will be unencrypted. This allows NAT routers to follow the FTP transaction. Pass a long using one of the values below

Don't attempt to use CCC.
Do not initiate the shutdown, but wait for the server to do it. Do not send a reply.
Initiate the shutdown and wait for a reply.

CURLFTPSSL_CCC_NONE

FTP

CURL *curl = curl_easy_init();
if(curl) {

curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/file.txt");
curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_CONTROL);
/* go back to clear-text FTP after authenticating */
curl_easy_setopt(curl, CURLOPT_FTP_SSL_CCC, CURLFTPSSL_CCC_ACTIVE);
ret = curl_easy_perform(curl);
curl_easy_cleanup(curl); }

Added in 7.16.1

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

CURLOPT_USE_SSL(3), CURLOPT_FTPSSLAUTH(3),

May 31, 2017 libcurl 7.64.0