Open port checker
Check whether up to 10 TCP ports of a public server accept connections, with common service ports one click away.
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The host you enter is sent to this site’s server, which tries to connect to the ports for you. Only public addresses can be checked, a few times a minute; queries are not stored.
About this tool
Check whether TCP ports on a public server accept connections from the internet. Use it after opening a port in a firewall or a cloud security group, to confirm that SSH, a website, remote desktop or a database is reachable from outside, or to make sure a port you meant to close really is closed. Common service ports can be ticked from a list.
Up to 10 ports can be checked at a time, and each one is tried for up to 3 seconds. The host you enter is sent to this site’s server, which tries the connections for you. Only public addresses can be checked, 6 times a minute and 60 times a day per visitor, so it cannot serve as a port scanner; queries are not stored.
How to use it
- Enter a “Host name or IP address”.
- Type the ports into “Ports (up to 10)”, separated by commas or spaces; ranges such as 8000-8005 work too. 80 and 443 are filled in.
- Or tick ports under “Common ports”, such as 22 SSH, 3306 MySQL or 3389 RDP.
- Select “Check ports”.
- Read the state of each port, “Open”, “Closed (refused)”, “No answer (filtered by a firewall?)” or “Unreachable”, and the time it took.
Common questions
What is the difference between “Closed” and “No answer”?
“Closed (refused)” means the server answered and refused the connection, usually because nothing is listening on that port. “No answer” means nothing came back within 3 seconds, which usually means a firewall drops the connection. “Unreachable” covers other network errors.
The service runs on my server. Why is the port not open here?
The check connects over the internet from this site’s server. The service may listen only on 127.0.0.1, or a firewall, a cloud security group or your network provider may block the port from outside.
Can it check UDP ports?
No. It only tries TCP connections, so UDP services, such as many game servers or DNS over UDP, cannot be checked.
Which address is checked when a domain has several?
Only the first public address the domain resolves to, preferring IPv4; the result shows it next to the host name. If any address of the name is private or reserved, the check is refused.
Why is the number of checks limited?
Each visitor may run 6 checks a minute and 60 a day, and one address accepts 20 checks a minute from all visitors together. Private, local and reserved addresses are refused. These limits keep the tool from being used to scan other people’s servers.
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