Network Troubleshooting for Beginners: Is the Door Open? (Ports)
September 15, 2025
Network Troubleshooting for Beginners: Is the Door Open? (Ports)
Introduction
A server’s IP address is like the postal address of an apartment building. But to reach the right apartment, you need the door number. In networking, these doors are ports.
- HTTP runs on port 80.
- HTTPS — on port 443.
- Mail, databases, and other services listen on their own ports.
If a port is closed or nothing is listening on it, the site won’t open — even if the server is “alive.”