🔍 Port Scanner

What is Port Scanning?

Port scanning is a technique used to identify open ports and services available on a network host. In networking, a port is a logical endpoint for communication — think of your IP address as a building's street address and ports as individual doors into that building. There are 65,535 available TCP ports, each potentially running a different service. Each port number corresponds to a specific service or protocol — for example, port 80 is used for HTTP web traffic, port 443 for HTTPS, port 22 for SSH, port 25 for SMTP email, and port 3389 for Remote Desktop Protocol (RDP).

When you run a port scan, the scanner sends connection requests to each specified port on the target IP address and observes the response. If the port accepts the connection, it's considered open and a service is actively listening. If the port rejects the connection or doesn't respond at all, it's considered closed or filtered. This information is fundamental to understanding your network's security posture — you can't protect what you don't know is exposed.

Why Scan Your Ports?

Regularly checking your own open ports is an essential part of maintaining good network security. Every open port is a potential entry point for attackers, and many security breaches begin with reconnaissance scans that discover services the administrator didn't realize were exposed. Here are the key reasons to scan your ports:

• Security Assessment – Identify potentially vulnerable services exposed to the internet. If you see port 3389 (RDP) open and you didn't intend it to be, that's a critical security risk that needs immediate attention.
• Firewall Testing – Verify your firewall is properly blocking unwanted connections. After configuring firewall rules, a port scan confirms they're working as expected from the outside.
• Server Configuration – Confirm your services are accessible as intended. If you've set up port forwarding for a game server on port 25565, a scan verifies it's reachable from the internet.
• Troubleshooting – Diagnose connectivity issues with specific applications. When a service isn't reachable remotely, a port scan quickly reveals whether the port is open or blocked.
• Compliance Verification – Many security frameworks require regular port audits to ensure only authorized services are accessible.

Common Ports to Know

Understanding what services run on common ports helps you interpret scan results. Port 21 is FTP (file transfer), port 22 is SSH (secure shell), port 25 is SMTP (outgoing email), port 53 is DNS (domain name resolution), port 80 is HTTP (unencrypted web), port 110 is POP3 (email retrieval), port 143 is IMAP (email retrieval), port 443 is HTTPS (encrypted web), port 445 is SMB (Windows file sharing — frequently targeted by malware), port 993 is secure IMAP, port 3306 is MySQL, port 3389 is RDP (Remote Desktop), and port 8080 is commonly used as an alternative HTTP port. If any of these ports are unexpectedly open on your public IP, investigate immediately — especially SMB (445) and RDP (3389), which are among the most commonly exploited services on the internet.

Understanding Results

Open: The port is accepting connections. A service is actively listening and accessible from the internet. This is expected for services you intentionally expose (like a web server on port 443) but concerning if unexpected.

Closed: The port is not accepting connections. Either no service is running on that port, or a firewall is actively blocking access. For most ports on a home connection, closed is the desired state.

Filtered: The port didn't respond at all, which typically means a firewall silently dropped the connection request rather than rejecting it. This is generally the most secure state because it doesn't even confirm the port exists.

Note: This scanner checks ports from our server to your public IP address. Results show what the outside world can see — which may differ from a local scan due to NAT, router firewalls, ISP-level filtering, or port forwarding rules. For a deeper understanding of port scanning concepts, check out our guide on understanding port scanning.