#First run this, to get port information (with the port you want to kill)
sudo lsof -i :3000
#Then run this, with <PID> replaced by the value in the column returned by previous command.
kill -9 <PID>
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