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* Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
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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), "