Does SFTP use port 21 or port 22?
SFTP usually uses port 22 but can be configured to run on nearly any port.
Port 22 is generally used for connection via SSH. SFTP is just one of protocols which can be run over SSH (others include virtual terminal). In fact, the SFTP is independent and can be run even without using SSH.
SFTP is sometimes called "Secure FTP" which leads to a common confusion with FTPS (which is called "Secure FTP" too).
SFTP - SSH File Transfer Protocol - usually runs over TCP port 22
FTP - plain, old file transfer protocol - usually runns over TCP port 21 (+ opens separate ports for data transfer)
FTP/SSL - FTP over TLS/SSL channel.
FTPS - same as FTP/SSL
Secure FTP - either SFTP or FTPS
@Paul A. Jungwirth Good question about 115. I think it states decimal 115 as that's an older, unsecure version of SFTP protocol, before SSH had been invented - from 1984 Simple File Transfer Protocol - https://tools.ietf.org/html/rfc913#page-1
SSH only suggests TCP:22 - but it's not required by any NAT algorithms like FTP does so it can be any port that admin sets up. Port 22 is only the default used in most installations.