When a computer system seeks to connect to another computer, the port serves as a communication endpoint
Ports are identified with positive 16-bit unsigned integers, ranging from 0 to 65535
| Port | Usage |
|---|---|
| 20 | FTP (send) |
| 21 | FTP (control) |
| 22 | SSH |
| 23 | TelNet |
| 25 | SMTP (send) |
| 53 | DNS |
| 80 | HTTP |
| 110 | POP3 (receive) |
| 143 | IMAP |
| 443 | HTTP (SSL) |
| 3306 | MYSQL |
| 6379 | Redis |
| 27017 | MongoDB |