| Port Number | Protocol | Description |
| 20 | ftp | FTP – Data Transfer Port |
| 21 | ftp | FTP – Control Port |
| 22 | ssh | Secure Shell (SSH) Remote Protocol |
| 23 | telnet | Telnet |
| 25 | smtp | Simple Mail Transfer Protocol |
| 53 | domain | Domain Name Protocol |
| 80 | http | Hypertxt Transfer Protocol |
| 110 | pop3 | Post Office Protocol |
| 123 | ntp | Network Time Protocol |
| 143 | imap | Internet Message Access Protocol |
| 220 | imap3 | IMAP version 3 |
| 389 | ldap | Directory Access Protocol |
| 443 | https | HTTP protocol over TLS/SSL |
| 465 | smtps | smtp over SSL |
| 587 | submission | submission port |
| 636 | ldaps | LDAP protocol over SSL |
| 993 | imaps | IMAP protocol over SSL |
| 995 | pop3s | POP3 protocol over SSL |
