Port Scanner Simulator
A learning simulation that shows how an online port scanner reports open, closed, and filtered ports.
This is an educational simulator. A web browser cannot open raw network sockets, so it cannot scan a real host. The results below are generated to teach you what each port state means and which service usually lives on each well-known port.
This tool runs entirely in your browser. No host is contacted and nothing is uploaded.
How to use this tool
- Type any host label in the first box. It is for display only and is never contacted.
- Enter the ports you want to test, or click a preset like common ports or web ports.
- Click Run simulated scan. Each port is matched to its well-known service and given a simulated state.
- Use Copy results to grab the table as plain text for your notes.
Because everything happens client side, you can experiment freely. This is the safe way to learn how to read the output of a real online port scanner before you ever run one.
How it works and why a browser cannot really scan
A genuine tool to test a local port connection or check open ports has to open a TCP socket to the target and watch how it responds. Web browsers deliberately block raw socket access for security, so no JavaScript page, including this one, can perform an actual network scan. Instead this web port tester maps each number you enter to the service that normally runs there and assigns a representative state so you can practice reading results.
In a real scan those three states come from the packets that return. An open port completes the handshake, a closed port returns a reset, and a filtered port stays silent because a firewall dropped the probe. Knowing the difference is the whole point of learning to read a scanner.
A real example
Say you test ports 22, 80, 443, and 3306 against a web server. A typical real-world result would show port 80 (HTTP) and 443 (HTTPS) as open because the site serves traffic, port 22 (SSH) as filtered because the firewall hides remote login from the public internet, and port 3306 (MySQL) as closed or filtered because a well-run database is never exposed directly. This simulator produces that same shape of output so the lesson sticks: public web ports open, management and database ports locked down.
Common questions
Does this online port scanner actually connect to my server?
No. It is a learning simulation. Browsers cannot open raw sockets, so no host is ever contacted and the states you see are generated locally for teaching.
What is the difference between closed and filtered?
A closed port means the host replied but no service is listening. A filtered port means no reply came back at all, usually because a firewall silently dropped the probe.
How do I really check open ports on my own machine?
Use a command line tool you control, such as nmap, or your operating system's built-in netstat. Only scan hosts you own or have written permission to test.
Why does the tool know the service for each port?
Well-known ports from 0 to 1023 are assigned to standard services by IANA, so 22 is SSH, 80 is HTTP, and 443 is HTTPS. The simulator looks those up to label each row.
Is unauthorized port scanning legal?
Scanning systems you do not own or have permission to test can be illegal and against acceptable use policies. This educational note is general guidance, not legal advice. Always get authorization first.