What is a port scanner?

A port scanner probes multiple TCP ports on a host to see which services accept connections — used for server administration and authorized security checks.

Is port scanning legal?

Scan only systems you own or have explicit permission to test. Unauthorized scanning of third-party networks may violate law or ISP acceptable-use policies.

What is an open port?

An open port accepts inbound TCP connections — a service is listening (web server, SSH, database, etc.).

What is a filtered port?

A firewall may drop probes without responding. This scanner reports closed when nothing answers; filtered behavior can look like closed from outside.

Why are some ports blocked?

ISPs block hosting on residential lines; firewalls deny by default; services may be stopped on the host.

What ports should be open on a web server?

Usually TCP 80 and 443. Admin ports like 22 should be restricted, not exposed broadly.

What is the difference between TCP and UDP?

This tool scans TCP ports. UDP (DNS, VoIP) requires different probes not covered here.

How do I close an open port?

Stop the service or block the port in OS firewall, cloud security group, or router. Re-scan to confirm.

Network Tools

Port Scanner Online

Scan multiple TCP ports on any IP address or hostname to identify open services, troubleshoot connectivity, and verify firewall configurations.

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