Free tool

Port check.

Probe specific TCP ports — or scan a preset — to see what's open, closed, or firewalled on any host.

Preset:
Try:

Enter a host above and pick ports or a preset.

Also free

HTTP status check →

Send a real request and inspect headers, redirects, body.

Next up

Monitor open ports with SiteWatch →

Get alerted when a port stops responding.

Only scan hosts you own or have permission to test. Aggressive scanning of third-party systems may violate their terms of service or applicable law.