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This option is not used when PROTOCOL is SSH, which doesn't use TLS/SSL. It is used when the PROTCOL is FTPS ("implicit" FTPS) or when UFTP requests explicit FTPS support.
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Explicit FTPS support was added to UFTP for Universal Agent 7.1.0.0. When an FTP server enables explicit TLS/SSL support, it allows clients to request encrypted sessions over the standard FTP port 21. This is different from implicit TLS/SSL support, which requires a connection to a unique, well-known port (990 by default) that ONLY accepts TLS/SSL-enabled client requests.
UFTP has always offered implicit FTPS support via the FTPS PROTOCOL value.
Because an FTP client may not always know whether the FTP server's port 21 is accepting SSL-enabled connections (i.e., it may only accept unencrypted, plain-text FTP sessions), explicit FTPS is not really a distinct protocol per se. Therefore, UFTP offers explicit FTPS support by applying new options and supported values to the existing FTP PROTOCOL value.
UFTP requests an explicit FTPS session using the ENABLE_SSL option or by prefixing the HOST option's value with ftpes://.
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