[USSD] is an interactive, menu-based technology supported by most mobile phones, to communicate with the computers of telephone operators, allowing the customer to perform certain operations or services autonomously and conveniently. It is accessible for everyone and for all types of mobile phones and without internet use.
USSD is a communication protocol for mobile phones.
It starts with an asterisk (*) and ends with a hashtag (#). It costs more but has great advantages and is used without internet. Mobile operators like unitel, movicel, etc need to have endpoints for callbacks. INACON assigns the short code, the short code is the USSD code, a great example, *111#. It is a session app, to continue with the connection you need to have the id of the session in which the operator assigns it right on the first connection. It has 2 prefixes, CON and AND. CON-> Defines that the app is still in connection. END->Sets the end of the connection.
Here I show how a USSD APP works, using prefixes (END and CON), menu navigation, pure API.