Linux Networking: Monitoring Connections and Finding Open Ports

Every system administrator and security enthusiast needs to know exactly what is happening on their network. Unrecognized open ports and unauthorized connections can expose your Linux servers to severe security risks. This text-based course guides you from networking fundamentals to hands-on command-line diagnostics. You will learn how to inspect active connections, detect listening ports, and troubleshoot network issues using standard built-in utilities. What you'll learn: Understand foundational networking concepts, including TCP/UDP ports, sockets, and connection states; Analyze active network connections using modern tools like ss and traditional utilities like netstat; Identify which processes are using specific network ports with lsof; Test remote port availability and establish basic connections using nc (netcat); Apply troubleshooting workflows to diagnose common connectivity and security issues on Linux; Implement basic security checks to detect unauthorized listening services. We begin with key terminology and the mechanics of network sockets before moving into practical command-line scenarios. Through clear, written explanations and real-world terminal examples, you will build a reliable diagnostic toolkit. This course is designed for beginners in Linux administration, cybersecurity, or system support who want to understand network diagnostics. No advanced networking experience is required. Start reading today to take control of your Linux network security and troubleshooting.