| **Application** | **TCP/UDP** | **Port** | **Notes** |
| HTTP | TCP | 80 | The Web |
| HTTPS | TCP | 443 | The Web, securely |
| Telnet | TCP | 23 | Terminal emulation |
| SSH | TCP | 22 | Secure terminal emulation |
| SMTP | TCP | 25 | Sending e-mail |
| POP3 | TCP | 110 | E-mail delivery |
| IMAP4 | TCP | 143 | E-mail delivery |
| FTP | TCP | 20/21 (active), 21 (passive) | File transfer |
| TFTP | UDP | 69 | File transfer |