Tools / Port checker
Is the port open?
Tested at once from Dallas, Amsterdam and London, with ping times from each.
Common ports
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<a href="https://privatebyte.com/tools/port-checker"><img src="https://privatebyte.com/tools/badge/port-checker.svg" alt="Ports checked with PrivateByte" height="22"></a>[url=https://privatebyte.com/tools/port-checker][img]https://privatebyte.com/tools/badge/port-checker.svg[/img][/url]How to fix a closed port
A port check tells you whether a service on your server can be reached from outside. When it cannot, work through these in order.
- Is the service running?
- On the server, run ss -tlnp (Linux) or netstat -ano (Windows) and look for the port.
- What address does it listen on?
- A service bound to 127.0.0.1 only accepts local connections. Bind it to 0.0.0.0 or the server's public address.
- Server firewall
- Allow the port in ufw, firewalld or Windows Defender Firewall, for example: ufw allow 3389/tcp.
- Provider firewall
- Check any security group or panel firewall in front of the server.
- Check again
- Closed means the server answered but nothing listens. No reply means a firewall drops the traffic.
Questions
What do open, closed and no reply mean?
Open: something accepted the connection. Closed: the host is up but nothing listens on that port. No reply: the connection got no answer at all, usually because a firewall drops it silently.
Why is my port closed when the service is running?
The service may be listening on localhost only (127.0.0.1), or a firewall such as ufw, firewalld or a cloud security group is blocking it. Check what address the service binds to, then the firewall rules.
Why test from three places?
A port can be open from one region and blocked from another, because of geo-blocking, upstream filtering or routing problems. Seeing all three at once tells you whether the problem is your server or the path to it.
Why can't I check port 25?
Our network blocks outgoing mail connections on ports 25, 465 and 587 to stop spam, so a check would always show no reply. Use your mail provider's own test, or telnet from another network.
Can I scan a range of ports?
No. This checks one port at a time, and checks are rate limited, so it cannot be used to scan other people's servers.
Run your service on a PrivateByte server: a firewall you control and every port yours to open.