cant run ng serve on 4200 and port is empty code example

Example 1: cancel ng server port

Using your terminal, find the PID of port 4200
netstat -ano | findstr :4200

Kill task by the PID Number (Replace 15940)
taskkill /PID 15940 /F

Example 2: how to close all ports angular

If you use 'Visual Studio Code' just click on the 'kill Terminal' on the top-right of the terminal and all the terminals ports will colsed