FTP
TCP 20: data transfer- Active: Client->Server
- Passive: Server->Client
TCP 21: control channelServer Config:
/etc/vsftpd.confDISALLOWED FTP users:
/etc/ftpusersServer Return Codes: https://en.wikipedia.org/wiki/List_of_FTP_server_return_codes
**TFTP has no auth and uses only UDP.