So I have an internal server that will be automatically grabbing files from an external FTP server via SFTP. It will be going through a stateful firewall. I was able to configure it with the help of a coworker, but I am trying to get an understanding of how a stateful firewall can cause difficulties in an SFTP connection. Is it dumb to say that SFTP = encrypted port 21 traffic ? Any helpful explanation or URLs to resources would be appreciated. Google was not being very helpful.