How WhatsApp Works?

There is a technical video on YouTube by WhatsApp software developer Rick Reed about the software infrastructure of WhatsApp. In basic logic, WhatsApp is a chat software where you can communicate with encrypted connections in written, audio and video form in the form of person-to-person, person-to-multiple-person or group chat. When WhatsApp is first installed on the device, it matches the person's phone number and WhatsApp account so that each number is registered in the system as a user. Since phone numbers are unique worldwide, no additional password protection is required during the registration phase.

The account verification process is carried out with an SMS to be sent to that phone. When your device communicates with WhatsApp servers for the first time, a token (security token) unique to your phone number is created with the SMS verification code you receive. The programme uses a customised XMPP protocol in its infrastructure. This protocol was also used in the past by programmes such as ICQ, AIM, Yahoo Chat and Google Talk. To automatically add contacts to the user's WhatsApp contact list, WhatsApp automatically retrieves all phone numbers from the device's address book and compares them with the central WhatsApp user database. In this way, WhatsApp contacts with saved phone numbers can be contacted.