How do I check if a port is open?

Enter the public host and TCP port above, then run the check. Open means our probe completed a TCP handshake; closed or timeout usually means a firewall or idle service.

What is an open network port?

An open port accepts TCP (or UDP) connections for a listening service. On the public internet that often means a web, mail, or remote-admin service is reachable.

How do I test TCP ports?

Use this port checker, or tools such as Test-NetConnection and nc, against a host you are authorised to probe. Always respect ownership and policy.

Why is a port closed?

Nothing may be listening, or a firewall may reject the connection (ECONNREFUSED or filtered timeout). Check local listeners, security groups, and ACL order.

Which ports are commonly used by web servers?

HTTP commonly uses TCP 80 and HTTPS uses TCP 443. Alternate web ports such as 8080 or 8443 appear on labs and reverse proxies.

What is Port Checker?

A free online tool that tests TCP reachability of a port on a public host for students and network administrators.

How does the Port Checker work?

After validating the target is public, our server opens a short TCP connection and reports open, closed, timeout, or error with latency.

How do I use the Port Checker?

Type a host, pick a port chip or custom port, then tap Check port. Try presets such as github.com:22 for practice.

Is this Port Checker free to use?

Yes. It is free with rate limits to keep the service fair for everyone.

Can I use the Port Checker on mobile?

Yes. The page works on mobile browsers for quick remote checks.

All free tools

Free tool

DNS & lookup

Port Checker

Probe a public hostname or IP on a TCP port. See open, closed, or timeout results for web, SSH, mail, and lab services.

Looks up public internet data for the target you enter. We do not store results.

Free tool

Knowing whether a TCP port answers from the internet separates firewall theory from reality. This free port checker performs a simple connect test from our servers to a public host so beginners, CCNA students, and network administrators can verify services such as 80, 443, 22, or 587. Use it after you place a server in a public CIDR block or publish an IPv4 example from subnetting practice—then confirm the port policy matches what you intended.

How to use the Port Checker

1
Enter a public hostname or IP (private addresses are blocked).
2
Choose a common port chip or type any port from 1 to 65535.
3
Tap Check port to see open, closed, timeout, or error with latency.

Why port checks belong in troubleshooting

An ACL or NAT rule can look perfect in a Cisco networking lab and still leave a port filtered on the path. Helpdesk teams waste hours restarting apps when the real issue is a closed inbound port. This tool only performs a TCP connect—it does not grab banners or exploit services—so students can practise safe verification on home networks they expose carefully and on public demonstration hosts.

Common web port example

Check google.com on port 443. You should see an open result if the path allows HTTPS. Compare with port 22 on the same host; many web properties keep SSH closed to the world. That contrast teaches beginners what “open” really means.

Guides and next steps

Privacy note

We attempt a short TCP connection from our servers to the public host and port you enter. Private targets are blocked. We do not store results.

Frequently asked questions

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