Port Scanner Network tools
Scan Configuration
Scanning in progress...
Initializing scan...
Scan Results
| Port | Status | Service | Description |
|---|
Security Note
Open ports can be potential security vulnerabilities. Ensure unnecessary services are disabled and properly secured.
Common Ports
HTTP: 80, HTTPS: 443, FTP: 21, SSH: 22, Telnet: 23, SMTP: 25, DNS: 53
Performance
Scanning many ports can take time. Start with common ports for faster results.
What is Port Scanning?
Port scanning is a network diagnostic technique used to discover which ports are open, closed, or filtered on a target system. Each port represents a specific service or application endpoint - like port 80 for HTTP web traffic or port 22 for SSH connections. Our port scanner helps network administrators, security professionals, and developers test connectivity and verify that services are properly configured and secured.
How Port Scanning Works
Port scanning operates by attempting to establish connections to specific port numbers:
- The scanner sends a connection request (SYN packet) to the target port
- If the port is open, the service responds with an acknowledgment (SYN-ACK)
- Closed ports typically respond with a reset (RST) packet
- Filtered ports may not respond at all (timeout)
- Results indicate which services are accessible on the target system
Common Port Numbers and Services
Web Services
- Port 80 - HTTP
- Port 443 - HTTPS/SSL
- Port 8080 - HTTP Alternate
- Port 8443 - HTTPS Alternate
Email Services
- Port 25 - SMTP
- Port 110 - POP3
- Port 143 - IMAP
- Port 587 - SMTP (Submission)
File Transfer
- Port 21 - FTP Control
- Port 22 - SSH/SFTP
- Port 23 - Telnet
- Port 445 - SMB/CIFS
Database Services
- Port 3306 - MySQL
- Port 5432 - PostgreSQL
- Port 1433 - MS SQL Server
- Port 27017 - MongoDB
Port Scanning Use Cases
Network Administration
- Service Verification: Confirm that required services are running and accessible
- Firewall Testing: Verify firewall rules are correctly configured
- Troubleshooting: Diagnose connectivity and service availability issues
- Documentation: Inventory network services and open ports
Security Assessment
- Vulnerability Detection: Identify potentially vulnerable services
- Compliance Checking: Ensure only authorized ports are open
- Attack Surface Analysis: Map exposed services and entry points
- Penetration Testing: Initial reconnaissance for security audits
Development and Testing
- Application Debugging: Verify services are listening on correct ports
- Environment Setup: Confirm development servers are properly configured
- Integration Testing: Test connectivity between distributed systems
- Container Verification: Check Docker or Kubernetes service exposure
Port States Explained
Open Ports
An open port actively accepts connections. A service is listening and responding to requests. This indicates the service is running and accessible from the network.
Closed Ports
A closed port is reachable but no service is listening. The system actively refuses connections, indicating the port is not in use but the host is responsive.
Filtered Ports
Filtered ports don't respond to probes. A firewall or security device may be blocking access, making it impossible to determine if the port is open or closed.
Security Best Practices
- Minimize Open Ports: Only expose services that are absolutely necessary
- Use Firewalls: Implement proper firewall rules to control access
- Regular Audits: Periodically scan your systems to detect changes
- Strong Authentication: Secure open services with strong passwords and encryption
- Keep Updated: Regularly update services to patch security vulnerabilities
- Monitor Logs: Watch for unauthorized connection attempts
Legal and Ethical Considerations
Important: Port scanning can be illegal if performed without authorization. Always ensure you have explicit permission before scanning any system you don't own. Unauthorized scanning may violate computer crime laws and result in serious legal consequences.
Common Port Scanning Scenarios
Web Server Check:
Target: webserver.com
Ports: 80, 443, 8080, 8443
Result: 80 ✓ 443 ✓ (Web services running)
Email Server Audit:
Target: mail.company.com
Ports: 25, 110, 143, 587, 993, 995
Result: Verify only required ports open
Frequently Asked Questions
Is port scanning illegal?
Port scanning your own systems or those you have permission to test is legal. However, scanning systems without authorization may violate laws like the Computer Fraud and Abuse Act (US) or similar legislation in other countries. Always get written permission.
Why do some ports show as filtered?
Filtered ports typically indicate a firewall or security device is blocking access. The packets are being dropped without response, which is a common security practice to avoid revealing information about the system.
How can I protect against port scans?
Use firewalls to block unnecessary ports, implement intrusion detection systems (IDS), keep services updated, use non-standard ports for sensitive services, and monitor logs for scanning patterns. Consider using port knocking for critical services.
Technical Implementation
Our port scanner uses PHP's fsockopen() function to attempt TCP connections to specified ports. The tool implements connection timeouts to efficiently scan multiple ports, rate limiting to prevent abuse, and validates target addresses to block scanning of private IP ranges. Results indicate whether each port is open (connection successful) or closed (connection refused).
Pro Tip: When securing systems, remember that security through obscurity (using non-standard ports) is not a replacement for proper security measures. Always implement strong authentication, encryption, and access controls for any exposed service.