Port 4200 is already in use

Using Angular CLI may happen "An unhandled exception occurred: Port 4200 is already in use." There are two ways that can solve.

1. kill -9 $(lsof -i tcp:4200 -t)
2. ng serve --port 4100 --open

The first method is to kill port 4200, but the second is to use a new port 4100.