Using an IP address or a domain name, this tool determines whether an internet socket port on an external server is open or blocked by a firewall. It is useful in diagnosis if port forwarding is setup correctly or if your server applications are being blocked by a firewall.
This tool may also be used as a port scanner to scan your network for ports that are commonly forwarded. It is important to note that some ports, such as port 25 SMTP (Simple Mail Transfer Protocol) and 465 Secure SMTP (often used by email providers such as Google-Apps for outbound email traffic), are often blocked at the ISP to prevent malicious activity.
While this may sound as a good thing, blocked ports by Firewalls of those hosting companies make it very difficult to diagnose outbound email problems, especially for applications like Joomla and WordPress.
For more a comprehensive list of TCP and UDP ports, check out Wikipedia article.
If you are looking for a software solution to help you configure port-forwarding on your network, contact Alicka development team.