Free Online Port Scanner

What is Port Scanning?

Port scanning is a network reconnaissance technique that identifies which ports on a host are open and accepting connections. Each networked service listens on a specific port number, so scanning reveals running services, verifies firewall rules, and uncovers potential security vulnerabilities.

Our port scanner uses Nmap, the industry-standard network scanning tool, to probe the specified ports on your target. It skips host discovery and uses aggressive timing to deliver fast, reliable results. The scan identifies whether each port is open, closed, or filtered, and attempts to determine the service running on each open port.

Common Network Ports

The table below lists the most commonly scanned network ports and the services typically associated with them:

Additional Ports

• Port 993 (IMAPS) -- IMAP over SSL, encrypted email retrieval.
• Port 995 (POP3S) -- POP3 over SSL, encrypted email retrieval.
• Port 1433 (MSSQL) -- Microsoft SQL Server database.
• Port 1521 (Oracle) -- Oracle database listener.
• Port 5432 (PostgreSQL) -- PostgreSQL database server.
• Port 5900 (VNC) -- Virtual Network Computing, a remote desktop sharing protocol.
• Port 6379 (Redis) -- Redis in-memory data store.
• Port 8080 (HTTP Alt) -- Common alternative HTTP port, often used for proxies and development servers.
• Port 8443 (HTTPS Alt) -- Common alternative HTTPS port.
• Port 27017 (MongoDB) -- MongoDB NoSQL database.

Open vs Closed vs Filtered Ports

When scanning ports, each port will be reported in one of three states:

• Open -- An application is actively listening and accepting connections on this port. This means the service is running and reachable from the network. Open ports are potential entry points and should only expose services that are intentionally public.
• Closed -- The port is accessible (not blocked by a firewall) but no application is listening on it. The host responds with a TCP RST packet. Closed ports are not an immediate security risk but indicate the host is reachable.
• Filtered -- A firewall, packet filter, or other network obstacle is blocking the probe, and Nmap cannot determine whether the port is open or closed. The packets are being silently dropped. This is generally the most secure state for ports that should not be publicly accessible, as it reveals no information to attackers.

A well-configured server will have only the necessary service ports open, with all other ports either closed or filtered. Database ports (3306, 5432, 27017, etc.) should never be open to the public internet. Administrative ports (22, 3389) should be restricted to known IP addresses. Regularly scanning your own servers helps ensure your firewall rules are working as expected. Use our IP Lookup tool to identify the organization and location behind any IP address you encounter in scan results.

Responsible Use

Port scanning is a legitimate and valuable network administration tool when used on systems you own or have explicit authorization to test. Scanning systems without permission may violate computer misuse laws in your jurisdiction. Always ensure you have proper authorization before scanning any target, and use this tool responsibly for security auditing, network troubleshooting, and verifying your own firewall configurations.

Frequently Asked Questions

Is port scanning legal?

Port scanning is legal when performed on your own systems or on systems where you have explicit permission from the owner. Unauthorized port scanning of third-party networks may violate computer misuse or unauthorized access laws depending on your jurisdiction. Always get written permission before scanning networks you do not own, and limit scans to the scope of your authorization.

What ports should be open on a web server?

A typical web server should have port 80 (HTTP) and port 443 (HTTPS) open for serving web traffic. Port 22 (SSH) should be open only for administrators and ideally restricted to specific IP addresses using firewall rules. All other ports -- especially database ports (3306, 5432), management ports (3389), and file sharing ports (445) -- should be closed or filtered on a production web server.

How do I close an open port?

To close an open port, you can either stop the service or application that is listening on that port, or configure your firewall to block incoming connections to it. On Linux, use systemctl stop servicename to stop a service, or use ufw deny PORT or iptables rules to block the port at the firewall level. On Windows, use the Windows Firewall settings or netsh commands to block specific ports.