UsingSFTP is a read-only Boolean property that indicates if a secure FTP connection is in use for the client session. 

UsingSFTP is updated at various points in an FTP protocol exchange. In Connect, UsingSFTP is set to True when UseTLS contains a value that indicates use of TLS for the socket transport. In Login, UsingSFTP is set to False until successful completion of the authentication process and protocol exhanges for TLS negotiation. 

The value in UsingSFTP is used at various points in the FTP protocol exchange to determine if additional commands are required to configure the control or data channels for the FTP session. 

During processing in the Get and Put methods, UsingSFTP determines the corresponding value for the PassThrough setting for an IOhandler that uses a secure transport. 

UsingSFTP also determines if use of the SendPBSZ command is allowed on the control channel for the client session.