How To Make Whatsapp Always Online on Android
1. In your android device go to Settings -> Display -> Screen Timeout, and here select Screen turns off automatically.
2. Now from the drop down list you will select the option none.
3. With this your mobile screen will now never go to sleep mode till you press the lock button.
4. Now open your whatsapp with mobile data or wifi enabled and leave your android as such.
5. As your screen is not going to sleep and till that time whatsapp will be running in your device with the internet connection and the app will stay online.