📘 03-06: Ports & Protocols Reference¶
📌 Port Number Ranges¶
| Range | Name | Use |
|---|---|---|
| 0–1023 | Well-known | Standard services (HTTP, DNS, SSH) |
| 1024–49151 | Registered | Vendor/app-specific |
| 49152–65535 | Dynamic/ephemeral | Temporary client-side ports |
A socket = IP address + port (e.g., 192.168.1.5:443).
📌 Must-Know Ports (N10-008)¶
| Port | Protocol | Purpose |
|---|---|---|
| 20/21 | FTP | File transfer (data/control) |
| 22 | SSH / SFTP / SCP | Secure shell & file transfer |
| 23 | Telnet | Remote CLI (insecure) |
| 25 | SMTP | Send email |
| 53 | DNS | Name resolution |
| 67/68 | DHCP | IP configuration |
| 69 | TFTP | Trivial file transfer |
| 80 | HTTP | Web (unencrypted) |
| 110 | POP3 | Retrieve email |
| 123 | NTP | Time synchronization |
| 143 | IMAP | Retrieve email (sync) |
| 161/162 | SNMP | Network monitoring/traps |
| 389 | LDAP | Directory services |
| 443 | HTTPS | Web (TLS) |
| 445 | SMB | File/printer sharing |
| 636 | LDAPS | Secure LDAP |
| 993 / 995 | IMAPS / POP3S | Secure email retrieval |
| 3389 | RDP | Remote desktop |
📌 Secure vs. Insecure Pairs¶
| Insecure | Secure replacement |
|---|---|
| Telnet (23) | SSH (22) |
| HTTP (80) | HTTPS (443) |
| FTP (20/21) | SFTP (22) / FTPS |
| SNMPv1/2c (161) | SNMPv3 |
Tip
Key idea — Memorize the well-known ports and their secure equivalents. Ports identify the application; a socket (IP:port) uniquely identifies an endpoint of a connection.
See also: Core Protocols & Their Ports, Secure Protocols & Encryption
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