Don't try to learn every port :) Just learn the top ones here.
Port numbers under 1024 are privileged ports that require admin or root to bind
| Protocol | Plaintext (Insecure) Port | Secure or Encrypted Port | Notes |
|---|---|---|---|
| HTTP | 80 | 443 | TLS 1.2 or 1.3 required (not SSL) |
| LDAP | 389 | 636 | LDAPS uses TLS wrapper |
| FTP | 21 | 22 (SFTP over SSH) | FTPS uses TLS. SFTP uses SSH |
| SMTP | 25 | 465 (SMTPS), 587 (STARTTLS) | SMTPS is old, STARTTLS is new |
| IMAP | 143 | 993 | TLS encrypted |
| POP3 | 110 | 995 | TLS encrypted |
| DNS | 53 UDP | DNSSEC provides integrity | |
| SNMP | 161 or 162 | Only v3 is encrypted (same port) | |
| SSH | 22 | Encrypted by default | |
| RDP | 3389 | Can use TLS for encryption | |
| RADIUS | 1812 or 1813 | 2083 | Can use TLS for encryption |
| Kerberos | 88 | Encrypted by default | |
| IKE | 4500 | Encrypted by default |