Final answer:
In Linux, network ports can be found using netstat, lsof, or ss commands. Commonly used ports include Port 22 (SSH), Port 80 (HTTP), and Port 443 (HTTPS).
Step-by-step explanation:
To find network ports in Linux, one can use several commands. The most common command is netstat, which can be used to display network connections, routing tables, and interface statistics. For example, the command netstat -tuln will list all TCP and UDP ports that are currently listening for incoming connections.
Another tool is lsof, which stands for 'list open files' and can show which ports are being used by which processes with the command lsof -i. Finally, ss is another utility that can be used to dump socket statistics and can replace netstat. The command ss -tuln will similarly display open TCP and UDP ports.
Three network ports that are commonly used by Linux servers for various applications or services include:
Port 22: Used by SSH (Secure Shell) for secure remote logins and file transfers.
Port 80: Used by HTTP (HyperText Transfer Protocol) for web server communications.
Port 443: Used by HTTPS (HTTP Secure) for encrypted web server communications.