Why scan ports
Every network service on a server listens on its own TCP port: SSH on 22, the web server on 80 and 443, MySQL on 3306. The scanner tries to connect to each port in the list and shows which ones are reachable from the internet.
- Security — databases, Redis or control panels should not be open to the whole world. If you see such a port open, restrict access with a firewall.
- Setup — after launching a new service, make sure its port is actually reachable from outside.
- Troubleshooting — site won’t load? Check whether the server responds on ports 80 and 443.
Acceptable use
Only scan servers you manage yourself or have permission to test. The tool only checks TCP connections; it sends nothing to services and does not test for vulnerabilities. Private and reserved IP addresses are not scanned. For an in-depth audit, install nmap on your own VPS.