We need port forwarding as we want to run a server behind the NAT firewall/router. Port on your router must be opened to run web server and other services like Remote Desktop, FTP server, SMTP server, SSH server etc. Some common ports are as below :
| Common Ports | |
|---|---|
| FTP | 21 |
| SSH | 22 |
| Telnet | 23 |
| SMTP | 25 |
| DNS | 53 |
| HTTP | 80 |
| POP3 | 110 |
| IMAP | 143 |
| Other Applications | |
| Remote Desktop | 3389 |
| PC Anywhere | 5631 |