03 June 2022

Android Emulator: Connecting to Localhost

I often use the Android Emulator to do testing on a Xamarin Forms app, or Cordova, or something of the sort.
It’s a long round trip to point at test when you want to debug the backend behaviour, so let’s point it at local dev!

The Android Emulator maps 10.0.2.2 to localhost, so can we just do that? In Kestral, yes!
I changed my Xamarin Forms app to point at http://10.0.2.2:5042 (my Kestral backend) and it Just Works.

Wonderful, but…what if we’re working with IIS?

IIS = Intrinsically Irritating Server #

Here’s the process I found after much Stack overflow (but essentially this one)

• Close VS
• Getting Invalid Hostname? Need to edit: \.vs\<project-name>\config\ApplicationHost.config
• Find <bindings protocal="http" line
• Copy the Http line and replace localhost with *

  Request from emulator isn’t coming from localhost, it’s coming from 10.0.2.2 or some redirection, so need to allow it in IIS (since it’s first in the chain)
  EDIT: May not need to copy, might be able to just set it to ":<port>:" (no stars)

• Open VS AS ADMIN (or you’ll get “can’t connect to IIS server”)
• Confirm by visiting that address in emulator browser

EDIT: Sept 2022
This tends to fail to run on PC restart (unable to parse hostname)
Changing back to localhost and running, then stopping and making it * again works…Weird, but fine.