Use '--port' to specify a different port. code example

Example 1: Port 4200 is already in use. Use '--port' to specify a different port

sudo lsof -t -i tcp:4200 | xargs kill -9

Example 2: 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 3: Use '--port' to specify a different port.

ng serve --open --port 4201