[Fixed] ng server – listen EACCES: permission denied 127.0.0.1:4200

Issue

I have no problem in do ng serve using 127.0.0.1:4200.

But today, when I do ng serve An unhandled exception occurred: listen EACCES: permission denied 127.0.0.1:4200

Is there a way to solve this problem permanently?

Solution

It sounds like your port is taken already.
You should kill the use in port 4200.
What operating system do you have?