Why is my Web API server refusing to accept calls from Android?

Question

I can access my Web API server from a Windows app without problems. From Android, though, is a different story

Why would that be?

Is "localhost" the wrong thing to use (in the URL)? Should I use the name of the computer instead?

Does the string (passed literally as "http://localhost:28642/api/Departments/GetCount?serialNum=4242") need to be verbatimized?

What is the difference between a Windows app calling a REST method, and an Android app calling the same REST method, that would cause the latter to fail (connection refused)?

Answer 1

Referencing "localhost" to refer to your local machine doesn't work on the Android emulator; you need to use a special IP which the emulator will forward on to the host machine. You need to replace localhost with 10.0.2.2, as per this answer.

If you're testing this on a physical device (rather than the emulator) you'll need to use your machines IP on the local network.