Appendix D — Ports and protocols reference
Ports worth recognising
| Port |
Protocol |
Service |
| 20 / 21 |
TCP |
FTP (data / control) |
| 22 |
TCP |
SSH / SFTP |
| 23 |
TCP |
Telnet (unencrypted — avoid) |
| 25 |
TCP |
SMTP (mail between servers) |
| 53 |
UDP + TCP |
DNS (TCP for large answers — must be open!) |
| 67 / 68 |
UDP |
DHCP (server / client) |
| 69 |
UDP |
TFTP |
| 80 |
TCP |
HTTP |
| 110 / 143 |
TCP |
POP3 / IMAP (mail retrieval) |
| 123 |
UDP |
NTP (time sync) |
| 161 / 162 |
UDP |
SNMP (monitoring) |
| 179 |
TCP |
BGP |
| 389 / 636 |
TCP |
LDAP / LDAPS |
| 443 |
TCP + UDP |
HTTPS (UDP = HTTP/3 / QUIC) |
| 445 |
TCP |
SMB (Windows file sharing) |
| 465 / 587 |
TCP |
SMTP submission (sending mail) |
| 500 / 4500 |
UDP |
IPsec VPN |
| 853 |
TCP/UDP |
DNS over TLS / QUIC |
| 993 / 995 |
TCP |
IMAPS / POP3S |
| 1194 |
UDP |
OpenVPN |
| 1433 / 1521 |
TCP |
MS SQL Server / Oracle |
| 3306 |
TCP |
MySQL / MariaDB |
| 3389 |
TCP |
RDP (Windows remote desktop) |
| 5432 |
TCP |
PostgreSQL |
| 5353 |
UDP |
mDNS (.local discovery) |
| 6379 |
TCP |
Redis |
| 8080 / 8443 |
TCP |
HTTP / HTTPS alternates |
| 27017 |
TCP |
MongoDB |
| 51820 |
UDP |
WireGuard VPN |
Generated from real-life-guide-v1.md · 8 Oct 2026 16:36
