"Invalid Host header" when running Angular/cli development server c9.io
Solution 1:
The --disable-host-check flag works fine if you need to run from Cloud9.
I use the following command:
ng serve --open --host $IP --port $PORT --disable-host-check
Solution 2:
In angular.json, add the following under architect -> serve -> options
"disableHostCheck": true
Got the answer from this Github Issue Page