PORT
CHECK.
Confirm whether specific TCP ports are reachable from an external point of view. The tool does not read banners, does not run NSE scripts and never tries to authenticate.
Use it on assets you manage or are authorized to test. Limits: up to 8 ports per check, up to 5 checks per minute per source address and a 3.5 s timeout per port. Port 25 is not tested. IPv4 only: the test infrastructure cannot open outbound TCP connections over IPv6.
Before an external check starts, let the automatic Cloudflare Turnstile validation finish.
Result as seen from the Cloudflare edge. The rating shows exposure risk; it does not confirm a vulnerability. An open port can be intentional: the goal is to highlight what deserves a review. Hosts behind Cloudflare itself may show up as RESTRICTED.
SHOW JSON RESPONSE
Frequently asked questions
What do OPEN, CLOSED and TIMEOUT mean?
OPEN: the TCP connection was accepted. CLOSED: the host refused the connection on that port. TIMEOUT: there was no answer within 3.5 seconds, which usually means a firewall is dropping the packets.
Why is the port closed if the service is running?
The service may listen only on localhost or the internal network, or a firewall, the router (missing port forwarding) or the provider's CGNAT may block access from outside.
Why is port 25 not tested?
The test infrastructure does not allow outbound connections on port 25 (SMTP), a common anti-spam restriction. Test SMTP on port 587 or 465, or from another server.
Can I test IPv6?
No. The check runs on the Cloudflare edge, which cannot open outbound TCP connections over IPv6. Hostnames are tested over IPv4. For IPv6, run it from a machine with IPv6: nc -6 -vz <address> <port> (Linux/macOS) or Test-NetConnection -ComputerName <address> -Port <port> (Windows).
How many ports can I test, and how often?
Up to 8 ports per check and a few checks per minute, with anti-abuse validation. Use it only on assets you manage or are authorized to test.