Complete Guide to Port Checking
What is a Port?
In computer networking, a port is a virtual point where network connections begin and end. Ports allow computers to distinguish between different types of traffic - web pages (port 80), emails (port 25), file transfers (port 21), etc. There are 65,535 ports available, with the first 1,024 being "well-known ports" assigned to common services.
How to Use This Port Checker
- Enter the IP address of the device you want to check (e.g., your public IP or server IP)
- Enter the port number you want to test (see common ports below)
- Click "Check Port" to see if the port is open
Common Ports and Their Services
| Port Number |
Service |
Protocol |
| 20, 21 |
FTP (File Transfer Protocol) |
TCP |
| 22 |
SSH (Secure Shell) |
TCP |
| 25 |
SMTP (Email) |
TCP |
| 53 |
DNS (Domain Name System) |
TCP/UDP |
| 80 |
HTTP (Web Traffic) |
TCP |
| 110 |
POP3 (Email Retrieval) |
TCP |
| 143 |
IMAP (Email Retrieval) |
TCP |
| 443 |
HTTPS (Secure Web Traffic) |
TCP |
| 3306 |
MySQL Database |
TCP |
| 3389 |
Remote Desktop Protocol |
TCP |
Why Check Ports?
Port checking helps you:
- Verify if a service is running and accessible
- Troubleshoot network connectivity issues
- Check firewall configurations
- Ensure security by closing unnecessary open ports
Troubleshooting Port Issues
If a port shows as closed when it should be open:
- Check if the service is running on the target device
- Verify local firewall settings
- Check router/firewall port forwarding rules
- Contact your ISP if you suspect they're blocking the port
Security Considerations
Open ports can be security risks if not properly managed:
- Only keep necessary ports open
- Use strong passwords for services
- Keep software updated to patch vulnerabilities
- Consider using a VPN for sensitive services
Advanced Port Scanning
For more advanced users:
- Port ranges: Check multiple ports at once (requires specialized tools)
- Service identification: Determine what service is running on an open port
- Banner grabbing: Get version information from services
This tool provides basic port checking functionality. For comprehensive network analysis, consider professional network monitoring tools.