React native android connect backend service at localhost

There could be 2 cases to test this problem.

1. Use Device
2. Use Emulator

Key point is run below command

$adb reverse tcp:3001 tcp:3001

TEMPLATE: adb reverse tcp:{APPLICATIONPORT} tcp:{APPLICATIONPORT}

The first case is ipconfig inside pc and find local IP address like 192.168.1.4. Your url should like http://192.168.1.4:3001/user/register

If you use emulator, you should use following url like http://10.0.2.2:3001/user/register

These URLs worked me, after running adb reverse command.