How does WhatsApp receive messages?

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Tags

1. #wakes
2. #whenever
3. #background
4. #service
5. #server
6. #message
7. #which
8. #similar
9. #always
10. #phone
11. #messages
12. #sends
13. #notification
14. #friends
15. #receive
16. #received
17. #whatsapp