This is just my list of common TCP/IP ports so I don't have to search through some huge list.
| Port | Used for |
|---|---|
| 20, 21 | FTP |
| 22 | SSH |
| 25 | SMTP |
| 53 | DNS |
| 80 | HTTP |
| 110 | POP3 |
| 123 | NTP |
| 143 | IMAP |
| 443 | HTTPS |
| 445 | Microsoft Directory Services |
| 902 | VMWare Management Console |
| 1433 | Microsoft SQLServer |
| 3306 | MySQL |
| 3389 | Microsoft Terminal Server (RDP) |
| 5500+ | VNC server connecting to viewer |
| 5800 | VNC web interface |
| 5900+ | VNC viewer connecting to server |
For completeness, here are some other common ports that you might come across:
| Port | Used for |
|---|---|
| 23 | telnet |
| 68 | DHCP |
| 79 | finger |
| 113 | IDENT Steve Gibson article on why you see it - my install of ProFTPd did it until I specifically disabled it. |
| 119 | NNTP |
| 135, 137, 139 | Microsoft Networking |
| 161 | SNMP |
| 194 | IRC |
| 389 | LDAP |
| 500 | IKMP - used for VPNs |
| 1311 | Dell OpenManage's Web Server |
These are ports that you should never have open since they are favorite crack targets:
| Port | Used for |
|---|
/etc/services\WINDOWS\SYSTEM32\DRIVERS\ETC\SERVICES