What is a Network Port?

A network port is a virtual point where network connections start and end. Think of an IP address as the street address of an apartment building, and the port numbers as the different apartment numbers within that building. While the IP address gets data to the correct device, the port number ensures that the data gets to the correct application or service running on that device. Ports are managed by a computer's operating system and are numbered from 0 to 65535.

Common Port Numbers and Their Services

Certain port numbers are standardized for specific services, making it easy for devices to communicate.

• Port 80 (HTTP): Used for standard, unencrypted web traffic. When you visit a website with `http://`, your browser connects to the server on port 80.
• Port 443 (HTTPS): Used for secure, encrypted web traffic. This is the standard for almost all modern websites.
• Port 21 (FTP): File Transfer Protocol, used for transferring files between a client and a server.
• Port 22 (SSH): Secure Shell, used for secure remote login and other secure network services.
• Port 25 (SMTP): Simple Mail Transfer Protocol, used for sending emails.
• Port 3306 (MySQL): The default port for the popular MySQL database service.

What is Port Scanning?

Port scanning is the process of sending requests to a range of port numbers on a host to determine which ports are open and listening for connections. It's like knocking on every door in the apartment building to see who answers. The response, or lack thereof, from each port reveals its status.

Legitimate Uses of a Port Scanner

While it can be used by attackers to find vulnerabilities, port scanning is a critical tool for network administrators and developers.

• Network Security Auditing: System administrators scan their own systems to verify their security policies and ensure that no unintended ports are left open, which could be a potential vulnerability.
• Troubleshooting Network Issues: If a service is not working (e.g., a website won't load), a developer can scan the relevant port (like 80 or 443) to see if it's open and accessible from the outside world. This helps diagnose firewall or server configuration issues.
• Service Discovery: To discover what services are running on a particular server.

How This Port Scanner Works

A web browser, for security reasons, cannot directly attempt to open connections to arbitrary ports on a server. This would be a major security risk. To work around this limitation, our tool uses a free, public proxy API that can perform these checks on our behalf.

1. You enter a host and a list of ports.
2. For each port, our tool sends a request to a proxy service, asking it to try and connect to `host:port`.
3. The proxy attempts the connection. If the connection is successful (the port is open), it returns a success message. If the connection times out or is refused (the port is closed), it returns a failure message.
4. Our tool then displays this "Open" or "Closed" status to you in real-time.

Frequently Asked Questions (FAQs)

1. How do I use the Port Scanner?

Enter the domain name or IP address you want to scan. Then, enter a comma-separated list of port numbers. You can also use the preset buttons to quickly load common ports. Finally, click the "Scan Ports" button.

2. Is port scanning legal?

Scanning your own servers or servers you have permission to test is perfectly legal and a standard network administration practice. However, scanning servers without permission can be considered a precursor to a malicious attack and may violate the terms of service of your internet provider or even local laws. Use this tool responsibly.