How to view open ports on a machine?

• netstat -tulnp - Show TCP and UDP sockets listening on ports, with PID and process name.
• ss -tulnp - Similar to netstat, but faster and recommended for modern systems.
• lsof -i -P -n - List open internet files, including listening ports.
• nmap localhost or nmap 127.0.0.1 - Scan the local machine for open ports.

Usage examples:

# View listening TCP ports with PID
netstat -tulpn | grep LISTEN

# View listening ports for a specific process (e.g., Nginx)
ss -tulnp | grep nginx

# Find process using port 8080
lsof -i :8080

# Scan local host for open ports using nmap
nmap 127.0.0.1

Standard tools:

Command	Purpose
netstat	Network statistics
ss	Socket statistics
lsof	List open files
nmap	Port and network scanner