Port Reachability Check
Tests whether a single TCP port on a host you specify accepts connections, and reports the banner.
Opens one TCP connection to one port on one public host and reports what happened: connected, refused, or nothing at all. It answers the question a firewall change actually raises — is this reachable from outside — which you cannot answer from inside your own network.
Our server makes one TCP connection to the one port you name, with a three-second limit. It sends nothing, and reads only the banner a service volunteers in the first second. Public addresses only, ten checks a minute — this is not a scanner.
How to use it
Enter a public host
A domain or a public IP address. Your home or office server is fine if it has a public address; 192.168.x.x and its neighbours are refused.
Pick the port
The quick buttons cover the usual suspects — 22, 80, 443, 3306, 3389, 8080 — and any port number can be typed instead.
Read the three outcomes apart
Open means something answered. Closed means the host answered with a refusal — it is reachable and nothing is listening. No answer means the packet vanished, which is what a firewall dropping traffic looks like.
Common questions
Is this a port scanner?
No, and it is built so it cannot become one. One port per request, ten requests a minute, and public addresses only. Nothing is written to the port either — only the banner the service offers of its own accord is read, for one second.
It says open but I cannot connect
The port is reachable from our server, which does not mean it is reachable from you. A firewall that allows some source addresses, a captive network, or an ISP blocking the port on your side all produce exactly this.
Why can I not check 192.168.0.1?
Because our server is not on your network, so it could only ever reach its own 192.168.0.1. Refusing private ranges outright also stops this page being used to map somebody else’s internal network from the outside.
What is the banner?
The first bytes a service sends unprompted on connect — SSH, SMTP and FTP all announce themselves this way, often with a version number. HTTP does not, so port 80 usually shows nothing.
Feed it from
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