About SFTP File Transfers

The Secure Shell protocol alone was not designed to perform secure file transfers. Strictly speaking, it is not a file transfer protocol. Furthermore, traditional file transfer protocols, such as FTP, are not amenable to being channelled easily over Secure Shell as they require more than one socket connection per session.

To make secure file transfer possible over Secure Shell, it was necessary to implement a tool that could execute FTP commands and file transfers over a single socket connection. That tool is the SFTP protocol, which is layered on top of the Secure Shell protocol to move files securely between FTP client applications and their target hosts.

The Connectivity Secure Shell implementation of the SSH2 protocol includes an SFTP tool, making it possible for you to secure FTP connections configured and initiated with Hummingbird FTP, Hummingbird’s FTP client application, as well as with third-party FTP clients.

Overview of the SFTP File Transfer Process

Built into Connectivity Secure Shell is an SFTP proxy server which you can configure to listen on multiple listening interfaces (IP address and port combinations). It is through these listening interfaces that the SFTP proxy server accepts inbound FTP connections (both control and data connections) as would an FTP server. It then interprets the incoming FTP commands and executes them as SSH2 SFTP commands through a tunnel connection to an SFTP server launched by the Secure Shell server on the target host.

Once the connections are established, the files you send and retrieve move securely between the SFTP proxy server and the host’s SFTP server.