File Sharing

FTP uses TCP 21 for its control connection. File data travels over a separate connection, so a successful login does not prove transfers will work.

OpenSSH listens on TCP 22 by default. Its SFTP subsystem transfers files over SSH, not the historical protocol assigned port 115.

TFTP (Trivial File Transfer Protocol) runs on UDP 69 with no authentication and no directory listing. It exists for automated distribution — router firmware, PXE network boot, VoIP phone provisioning — where the client already knows the exact filename.

IANA assigns TCP 115 to the historical Simple File Transfer Protocol. Its SFTP abbreviation must not be confused with SSH File Transfer Protocol.

NetBIOS session service port for Windows file and printer sharing

SMB/CIFS (Server Message Block) protocol port for file and printer sharing

rsync protocol port for file synchronization and backup services

FTP data transfer over SSL port for secure FTP data transmission

TCP 990 is implicit-mode FTPS: the TLS handshake begins the moment the client connects, with no AUTH TLS negotiation. The explicit variant (port 21 + AUTH TLS) is more common today, but many older clients and appliances still default to 990.

Network File System protocol port for remote file access and sharing