ng server - listen EACCES: permission denied 127.0.0.1:4200

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

I have solved this issue by simply going to Control Panel\Network and Internet\Network Connections and then I disabled all the Hyper-V Connections/Adapters and I kept the ones I use like the Wifi and Physical Ethernet Adapter.

No restart needed. Once done, try to run your Angular app on 4200 and it should work.

For me happens after Windows 10 Update to build 2009.

There is a network adapter which is blocking your port.

For @p90n33r was Hyper-V.

For me was Wifi adapter before I use ethernet port.

Try disable any adapters to test it.

No restart needed.