Testing Ports

Verify that your port forwarding configuration is working correctly.

Testing ensures your services are accessible from the internet.

After configuring port forwarding, you need to test that external traffic can reach your server. This involves testing from inside and outside your network.

Using browser:

• `http://localhost:port`
• `http://192.168.1.50:port` (use your server's IP)

Using command line:

• `telnet localhost port`
• `nc -zv localhost port`

Purpose:

• Verify service is running locally
• Confirm service is listening on correct port
• Rule out local configuration issues

Using phone on mobile data:

• Disconnect from WiFi
• Try accessing via public IP: `http://YOUR_PUBLIC_IP:port`
• Ensures external access works

Using online port checkers:

• Various websites can check if ports are open
• Enter your public IP and port
• Check if port shows as open

Purpose:

• Verify port forwarding is working
• Confirm external accessibility
• Test from different networks

Port shows closed:

• CGNAT blocking port forwarding
• Double NAT configuration
• Firewall blocking
• Port forwarding rule not applied

Connection times out:

• Router blocking connection
• Service not running
• Firewall on server blocking

Connection refused:

• Service not listening on that port
• Wrong port in configuration
• Service crashed

1. Verify static IP hasn't changed
2. Check firewall on server (ufw, iptables)
3. Confirm service is running and listening
4. Test with different port
5. Check for ISP blocking of common ports
6. Verify not behind double NAT

• Port Forwarding Explained: How to Open Ports on Your Router
• Port Forwarding Explained: How It Works, Risks and Setup

• Networking Overview
• Port Forwarding

Last updated: 2026-06-19

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