Port Check
A free tool that checks whether a specific port on a target host is open (TCP reachable). To prevent misuse, only well-known ports are supported, and private/internal addresses can't be checked.
Port Check
Checks whether a specific port on a target host is open (TCP reachable). Only well-known ports can be selected.
Guide
What is a port check
It checks whether a specific port on the target server is reachable from outside. "Open" means a TCP connection succeeded on that port; "Closed" means the connection was refused or there was no response.
Supported scope
To prevent misuse, only well-known ports are supported, and private/internal addresses like 192.168.x.x and 10.x.x.x can't be checked.
Practical example and verification criteria
Port Check: First determine whether this page only calculates a format in the browser or the Tool Web server performs a DNS, port, or public-IP lookup. Do not mix a protocol or path into a hostname. Enter IP, MAC, and port values with the separators and ranges requested by the page, and confirm you are authorized to query the target.
Port Check: For a quick check, start with example.com:443 as a small input whose result relationship you can verify directly. Confirm that the input summary, units, and options match your intent before applying the tool to real values or a copy of the source; this reduces setup mistakes.
Port Check: DNS caches, firewalls, NAT, proxies, and the lookup server's location can make results differ from observations on your device or another network. Recheck the same target with operating-system commands or an authorized management console. Location data is approximate, and a port response alone cannot establish that a service is secure.
Port Check · Work record: For real work, record the input conditions, selected options, and result together. Do not assume the same state will remain after a refresh or device change. Preserve important results separately using copy, download, a screenshot, or another method the page supports, then reopen them in the target environment.
Port Check · Error check: If an error or unexpected result appears, reduce the input, run again with default options, and then change one condition at a time. Recording error messages and boundary values helps distinguish format issues, unsupported cases, and browser resource limits, and prevents an empty result from being mistaken for success.
Port Check · Scope of use: Check the page guidance for browser processing versus server lookup, storage location, and supported scope. Use sensitive source material or secrets only when strictly necessary. High-impact work such as legal, financial, or medical decisions or changes to an operational system requires current authoritative information and a separate verification process.