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Security & Network

Open Port Checker

Check if a specific port is open on any host. Tests TCP connectivity with timeout detection. Useful for debugging firewalls, servers, and network configurations.

What is Open Port Checker?

An open port checker tests whether a specific TCP port is reachable on a remote host. When a port is open, a service is listening and accepting connections. When it is closed, no service is listening. When it is filtered, a firewall is blocking the connection. This tool sends a check request to our backend API which attempts a TCP connection to the specified host and port, returning the result with latency information.

How to Use Open Port Checker

  1. 1

    Enter the host

    Type the domain name (example.com) or IP address (192.168.1.1) of the server you want to check. Do not include the protocol (http://).

  2. 2

    Set the port

    Enter the port number (1-65535) or click one of the common port presets: 80 (HTTP), 443 (HTTPS), 22 (SSH), 3306 (MySQL), etc.

  3. 3

    Click Check Port

    The tool sends a TCP connection test to the specified host and port. Results appear within a few seconds, including latency if the port is reachable.

  4. 4

    Review the result

    Open (green) means a service is listening. Closed (red) means no service is responding. If the check fails, command-line alternatives are shown for manual testing.

Features

  • Check any TCP port (1-65535) on any host or IP address
  • 12 common port presets with service names (HTTP, SSH, MySQL, etc.)
  • Connection latency measurement in milliseconds
  • Timeout detection for filtered/firewalled ports
  • Check history showing the last 20 results
  • Color-coded status: green (open), red (closed), yellow (error)
  • Command-line alternatives provided when API is unavailable
  • No software installation required -- works in your browser

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Frequently Asked Questions

What does "open" mean?+
An open port means a service (like a web server, SSH daemon, or database) is actively listening on that port and accepting TCP connections. This is expected for services you are running intentionally.
What does "closed" mean?+
A closed port means the host is reachable but no service is listening on that specific port. The host responds with a TCP RST (reset) packet.
What does "filtered" mean?+
A filtered port means a firewall or security device is silently dropping the connection attempt. You get no response (timeout). This is the most common state for ports blocked by cloud firewalls (AWS Security Groups, Cloudflare, etc.).
Can I check UDP ports?+
This tool checks TCP ports only. UDP port checking is unreliable over the internet because UDP is connectionless -- there is no handshake to confirm the port is open. For UDP, use nmap with the -sU flag from a command line.
Is my IP address logged?+
The port check is performed by our server, so the target host sees our server IP, not yours. We do not permanently log check requests.
Why does the check fail?+
Common reasons: (1) The host does not exist or is unreachable. (2) DNS resolution fails. (3) Your network blocks outbound connections. (4) The backend API endpoint is not yet configured. In all cases, the tool provides command-line alternatives.
What port should my web server use?+
Standard web servers use port 80 (HTTP) and 443 (HTTPS). Port 8080 is commonly used for development servers or proxies. Always run production sites on port 443 with TLS.
Can I scan multiple ports at once?+
This tool checks one port per request. For multi-port scanning, use nmap from the command line (nmap -p 1-1000 example.com). Mass port scanning without permission may violate terms of service or laws.