how block 3030 port from node for testing code example

Example 1: Port 3000 is already in use, but when I try to kill nothing is found

netstat -ano | findstr :3000
taskkill /PID "123" /F

Example 2: stop npm running on port 3000

netstat -ano | findstr :3000
taskkill /F /PID PID_of_port