When I try to hit my web app on port 8080 I get the following error
Bad Request - Invalid Hostname
HTTP Error 400. The request hostname is inval
I'm not sure if this was your problem but for anyone that's trying to access his web application from his machine and having this problem:
Make sure you're connecting to 127.0.0.1 (a.k.a localhost) and not to your external IP address.
Your URL should be something like http://localhost:8181/ or http://127.0.0.1:8181 and not http://YourExternalIPaddress:8181/.
When you connect to your external IP address, you connect to you from the internet, as if you were a stranger (or a hacker).
However when you connect to your localhost, you connect locally as yourself and the block is obviously not needed (& avoided altogether).