Open Port Checker
Check whether a common service port is open on any domain — from the public internet, in seconds. Pick a port, enter a hostname, and see if it's reachable.
Why a closed — or unexpectedly open — port matters
Every service your site depends on — the web server, mail, a database, a cache — listens on a specific TCP port. When that port stops accepting connections, the service behind it is effectively down, even if the machine itself is still running.
Ports fail the other way too: a database or admin port that should be firewalled off can end up exposed to the whole internet. Checking a port from the outside is the fastest way to confirm it's reachable exactly when it should be — and closed when it shouldn't.
How this port checker works
Pick a port from the list of common services and enter a hostname. We resolve the domain to its public IP, open a single TCP connection to that port, and report whether the handshake succeeds. Open means the service accepted the connection; closed means it was refused, filtered, or timed out.
For safety this is a connect-only test against a curated list of well-known ports: it opens the socket, records the result, and closes it immediately without sending or reading any data. It never touches private or internal addresses.
How do I check if port 443 is open?
Select 443 — HTTPS from the port list, enter your domain, and run the check. The tool connects to that exact port on your server's public IP and tells you whether it's open, closed, or filtered.
Why does a port show as closed when the service is running?
A port can be running yet still look closed from the outside if a firewall or security group blocks it, the service only listens on localhost, or your hosting provider filters that port. This checker tests from the public internet, so it sees exactly what your users (and attackers) see.
Which ports can I check?
For safety the tool checks a curated list of common service ports — web (80, 443, 8080, 8443), mail (25, 465, 587, 110, 143, 993, 995), databases (3306, 5432, 1433, 6379, 27017), and a few others like SSH (22), DNS (53), RDP (3389), FTP (21) and AMQP (5672). It won't scan arbitrary ports.
Can Narvin alert me if a port goes down?
Yes. Narvin can watch a specific TCP port every minute and alert you (email, Slack, and more) the moment it stops accepting connections — so a silent service failure never turns into unnoticed downtime.
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