IPTools UK

Port Checker

Check whether a single TCP port on a host is open — with strict abuse-prevention limits, no range scanning.

Acceptable use

Only check hosts and ports you own, manage, or otherwise have explicit permission to test. This tool checks one host/port combination at a time, is rate-limited, and must not be used for scanning or reconnaissance against systems you do not control.

About this tool

This tool attempts a direct TCP connection to the host and port you specify, using Cloudflare's Worker TCP Sockets capability, and reports whether the connection succeeded within a strict timeout. It is intended for diagnosing your own servers and services — for example, confirming a firewall rule or checking whether a newly deployed service is reachable.

How to use this tool

  1. Enter a hostname or IP address.
  2. Enter a single port number, e.g. 443 for HTTPS or 22 for SSH.
  3. Select "Check port".

Frequently asked questions

Why can I only check one host and one port at a time?
Scanning multiple ports or hosts in sequence is how automated port scanners work, and hosting that capability publicly would make this tool useful for reconnaissance against systems the user doesn't control. Restricting to a single host/port pair per request, combined with rate limiting, keeps this a legitimate diagnostic tool.
Why is port 25 blocked?
Port 25 (SMTP) is blocked to prevent this tool being used to probe for open mail relays, which is commonly associated with spam abuse.
What does "closed or filtered" mean?
It means no TCP connection could be established within the timeout. This could mean the port is genuinely closed, that a firewall is silently dropping the connection attempt (filtering), or that the host is unreachable.
How are ports 80 and 443 checked?
The Cloudflare Workers platform this site runs on does not allow raw TCP connections to ports 80 or 443 — it requires HTTP(S) traffic on those ports to go through a normal HTTP request instead. For those two ports only, this tool sends an HTTP HEAD request rather than opening a raw socket; any HTTP response (including an error status) confirms the port is open. Every other port is tested with a real TCP connection.

HTTP Headers

View your own request headers, or safely inspect the response headers, status code and redirect chain of any public URL.

DNS Lookup

Query A, AAAA, CNAME, MX, TXT, NS, SOA and CAA records for any domain using DNS-over-HTTPS, with full TTL and record detail.

IP Lookup

Look up an IPv4 or IPv6 address: version, approximate location, ASN, network organisation, reverse hostname and RDAP registration data.