01. What is a Port?
A port is a numeric identifier for a specific service. It acts like a digital door for your computer. Websites use Port 80. Secure logins use Port 22.
02. TCP vs UDP
TCP is reliable and checks for errors. It is used for web browsing. UDP is extremely fast but does not check for errors. It is used for video games and streaming.
03. The ss -tuln Command
This command lists all open listening ports. It pulls data directly from the Linux kernel. It is the fastest tool for network discovery.
04. Why Use This Tool?
Hackers use it to find open doors. You can use it to find hidden malware backdoors. It also helps you verify if your web server is running correctly.
05. Professional Tips
Use sudo ss -tulnp to see Process IDs. This shows exactly which program owns the port. Always switch from netstat to ss for modern Linux systems.
