Connect to your Android device according to this manual:
http://developer.android.com/tools/device.html
Issue following commands:
adb shell
netcfg
(deprecated, use ip link show or ifconfig instead)

It gives you output similar to following:
lo       UP                                   127.0.0.1/8   0x00000049 00:00:00:00:00:00
usb0     DOWN                                   0.0.0.0/0   0x00001002 66:f7:3e:fc:88:d3
sit0     DOWN                                   0.0.0.0/0   0x00000080 00:00:00:00:00:00
ip6tnl0  DOWN                                   0.0.0.0/0   0x00000080 00:00:00:00:00:00
rmnet0   DOWN                                   0.0.0.0/0   0x00001082 fa:2f:d1:49:37:fd
rmnet1   DOWN                                   0.0.0.0/0   0x00001082 62:31:e3:93:3d:a0
rmnet2   DOWN                                   0.0.0.0/0   0x00001082 ba:2a:1c:03:ec:68
p2p0     DOWN                                   0.0.0.0/0   0x00001002 42:b0:fa:82:17:46
wlan0    DOWN                                   0.0.0.0/0   0x00001002 40:b0:fa:82:17:46

Use MAC address of usb0 or wlan0 as HWID.

 

To get the MAC address for WLAN, you need to enable WiFi on the device.

You can also find MAC address using graphical interface - in settings of the device (this is device specific so you will have to search little bit).


Android 6

Android version 6 removes programmatic access to the device’s local hardware identifier for apps using the Wi-Fi and Bluetooth APIs. You can use the serial number or IMEI of your device as Hardware ID for license generation. For more information see also this issue Android licensing no MAC based HW ID.

[https://developer.android.com/about/versions/marshmallow/android-6.0-changes.html#behavior-hardware-id]