Check whether selected TCP services are reachable on an authorised public IP address or domain.
A TCP port check shows whether a destination accepts connections on specific service ports from the internet. It is useful after DNS resolves correctly but a website, mail server or remote desktop session still fails to connect.
This tool attempts a short TCP connection from the Zerolink server and classifies each port as open, closed or filtered. It tests reachability only — it does not scan for vulnerabilities, brute-force credentials or probe systems you are not authorised to assess.
For a broader workflow, start with DNS lookup, then use ping or traceroute if the host itself appears unreachable before checking individual ports here. Compare measured throughput with the internet speed test when the service is slow but ports look open.
Test only the service ports related to the failure, then widen the check only if the host itself is reachable.
Enter a destination and a comma-separated list of ports.
Check only systems you own or have explicit permission to test. Results originate from the Zerolink server.
Interpret results carefully
The destination accepted the TCP connection. Confirm that the exposed service is intentional, updated and access-controlled.
The host responded but refused the connection, normally because no service is listening or a firewall rejected it.
No response arrived before timeout. A firewall or network policy may be silently dropping the connection.
Restrict administration and database services to trusted addresses or a VPN. Use the Ping and Reachability Tool when the entire destination appears unreachable.
An open result means the destination accepted a TCP connection on that port. It does not confirm that the service is secure or correctly configured.
Closed usually means the host actively refused the connection. Filtered means no response arrived before timeout, commonly because a firewall silently dropped the request.
The connection originates from the Zerolink hosting server. Firewalls, routing and geographic policies can produce different results from another network.
Only ports required by the intended public service should be exposed. Common examples are 80 and 443 for websites; administrative and database ports should usually be restricted.
No. It confirms reachability only. Vulnerability assessment requires authorised service identification, configuration review and security testing.
No. This release tests TCP reachability only. UDP services such as DNS or some games require different diagnostic methods.
The limit keeps checks focused and prevents misuse for broad unauthorised scanning. Run additional batches if you need to review more ports on the same host.
Both work. A domain is convenient, but the tool resolves to an IP before connecting. If DNS recently changed, compare results against the direct address as well.
Test authorised public ports for VPN, mail or camera viewers hosted behind a Zerolink connection in Haryana. Always limit checks to systems you own or have permission to assess.