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Port Check

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Check whether a specific TCP port on a host accepts connections from the internet.

Port Check

Hostname or public IP address

TCP port number

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Try:

How it works

The server attempts a single TCP connection to the given port. A completed handshake means open; a reset means closed; no answer usually means filtered by a firewall.

Safeguards & responsible use

  • Server-side input validation: only syntactically valid hostnames and IP addresses are accepted.
  • Private, loopback, link-local and reserved address ranges are blocked to protect internal infrastructure.
  • Per-client rate limiting and request timeouts.
  • One port per request; no range scanning.

Frequently asked questions

Why does my port show as closed when the service is running?

Check the firewall, router port forwarding and that the service listens on all interfaces, not only on localhost.

Can I check UDP ports?

UDP is connectionless, so “open” cannot be confirmed reliably without a protocol-specific reply. The first version checks TCP only.