How It Works

The checker performs a lightweight TCP connection attempt to your site’s hostname on each port you provide. A successful connection indicates something is listening on that port (for example, a web server, a mail submission service, or an application gateway). If the connection is refused or times out, the tool reports the port as closed or unreachable.

Under the hood, a TCP “open” result means the three-way handshake completed. This does not automatically guarantee the application is healthy; it only confirms that the network path is working and that an application is accepting connections. For HTTP services, you should still follow up with a normal browser request or an HTTP status check to confirm correct responses and headers.

What the result means

• Open (listening): The TCP handshake completed. A service is reachable on that port.
• Closed / refused: The host responded but nothing is accepting connections on that port, or an edge component is explicitly rejecting it.
• Timed out: No response in the selected timeout window. This can indicate filtering, routing issues, rate limiting, packet loss, or upstream firewalls that silently drop traffic.
• Resolution note: If the hostname cannot be resolved to an IP address, the report includes a hint so you can fix DNS first.

Why latency matters

Measuring approximate connection time helps you interpret failures. An immediate “refused” often points to a closed port, while a long delay or timeout may indicate filtering or network congestion. In incident response, this small detail can save time by steering you toward firewall rules, routing paths, or load balancer health checks sooner.

Key Features

Multi-port input with ranges

Paste ports separated by commas, spaces, or new lines. You can also use ranges like 8000-8005 to test consecutive ports quickly when you run multiple services, micro-frontends, or container apps. The tool normalizes the list, removes duplicates, validates port limits, and processes ports in order.

Connection timeout control

Select a timeout that matches your troubleshooting scenario. Short timeouts are useful for quick checks on stable networks, while longer timeouts help avoid false negatives when your infrastructure is under load or when routes include additional inspection layers.

Latency measurement per port

Each port check includes an approximate connection time. This is helpful when you need to differentiate between an immediate refusal (often a closed port) and a slow or filtered path (often a timeout or aggressive firewall inspection). Over time, collecting these measurements can also highlight regressions after changes to proxies or routing.

Copy-ready and downloadable report

Beyond the on-screen table, the tool generates a plain-text report suitable for ticket comments, incident channels, or email. Copy it with one click or download it as a text file for audit trails. The report includes the host, the timeout setting, the timestamp, and each tested port with a clear status label.

Common port guidance

Port numbers are simply “doors” that route traffic to the correct service. While every environment is different, it helps to recognize the usual suspects. Web traffic typically uses 80 (HTTP) and 443 (HTTPS). Mail setups often involve 25, 465, and 587. Administrative services sometimes use 22 (SSH) or 3389 (RDP) and should usually be protected by allow-lists, VPNs, or zero-trust access gateways rather than exposed broadly.

Safe-by-design target

The checker is designed for troubleshooting your own website. It targets the current site host, which helps avoid accidental scanning of unrelated systems and keeps the tool focused on operational diagnostics rather than broad network reconnaissance.

Use Cases

• After moving hosts: Validate that HTTP/HTTPS ports are reachable right after a DNS cutover and before you announce the change.
• Firewall change verification: Confirm that an allow-list update actually opened the expected ports for your users, partners, or monitoring systems.
• Reverse proxy troubleshooting: Check whether an upstream service port is listening after a container restart, a system update, or a process crash.
• Mail deliverability debugging: Verify whether submission ports appear reachable when configuring outbound email or troubleshooting authentication failures.
• Monitoring confirmation: When an uptime alert fires, quickly validate reachability and attach a report to the incident record.
• Staging vs production parity: Compare which ports are exposed across environments to reduce surprises during release day.

In real operations, port status is only one layer of the story. A port can be open while the application is returning errors, and a port can be closed intentionally because an edge component is meant to terminate connections elsewhere. Use this tool to confirm the “network basics” first, then validate protocols (HTTP, SMTP, SSH) and application logs as the next steps.

If you are troubleshooting systematically, a simple workflow often works well: (1) confirm hostname and DNS resolution, (2) test the expected ports, (3) compare results across networks or regions if you suspect filtering, and (4) collect a report to share with the team. This approach keeps incidents calm and repeatable, even when many people are asking for updates at once.

Optimization Tips

Start with the ports you expect to expose

Begin with what your architecture should expose publicly. For most websites, that is 80 and 443. If you run APIs behind a gateway, you may only need 443. If you expose a custom port for a specific service, document why it must be public and ensure it is monitored.

Use a realistic timeout

A 2–3 second timeout is often a sweet spot. Very low timeouts can produce false “timeout” results on busy networks, while very high timeouts slow down troubleshooting. If your results are inconsistent, increase the timeout slightly and rerun. Consistency is more valuable than absolute speed during incident response.

Interpret “timeout” carefully

A timeout does not always mean a service is down. Firewalls commonly drop packets instead of rejecting connections. Dropped packets lead to timeouts. If you expect a port to be open but see timeouts, review security groups, WAF rules, upstream load balancers, and whether the service is bound to the correct interface.

Reduce exposure as a default

As a general security practice, expose only what you need. Keep databases and internal services private. If you must expose administration endpoints, restrict them with allow-lists, VPN access, or a dedicated access proxy. A clean port check that shows only the intended ports open is a positive signal for both reliability and security.

Record before/after results during changes

When you make a change—like moving to a new load balancer, migrating to a different hosting provider, or updating firewall rules—run a port check before and after. Keeping that “before/after” record makes rollbacks and postmortems easier, and it speeds communication with support or infrastructure teams.