Reading the results
Three possible results per port: open means something accepted the connection; closed means the host actively refused it, which still confirms the host itself is reachable; filtered means nothing came back at all within the timeout, almost always because a firewall is silently dropping the traffic rather than rejecting it. A closed port and a filtered port both mean "you can't connect," but they tell you different things about what's actually happening on the network path.
Why this only checks specific ports
This tool checks a chosen list of ports, capped at 20 per scan, rather than scanning an open range. That's intentional — it's built for confirming whether a specific expected service is reachable (did that MySQL port actually open after the firewall change, is SSH still exposed when it shouldn't be), not for broad reconnaissance scanning.
Frequently asked questions
What's the difference between "closed" and "filtered"?
Closed means the host actively refused the connection. Filtered means no response came back at all, usually a firewall silently dropping it.
Why can't this check every port at once?
By design, it checks a limited list per scan rather than a full range — built for confirming specific services, not broad scanning.
Is it legal to scan a host I don't own?
It can violate a provider's terms of service and, in some places, carry legal risk, even though the technique itself is benign. Only scan hosts you own or have permission to test.