Port and protocol

• 20/21 (TCP) → FTP
• 22 (TCP) → SSH
• 23 (TCP) → Telnet
• 25 (TCP) → SMTP
• 80 (TCP) → HTTP
• 161 (TCP/UDP) → SNMP
• 389 (TCP/UDP) → LDAP
• 443 (TCP) → SSL/TLS(HTTPS)
• 445 (TCP) → SMB
• 3389 (TCP) → RDP

References

• https://www.stationx.net/common-ports-cheat-sheet/
• https://web.archive.org/web/20240315102711/https://packetlife.net/media/library/23/common-ports.pdf
• https://nullsec.us/top-1-000-tcp-and-udp-ports-nmap-default/