There is such task - login user, to obtain from him the text information and give him back the result of processing this information. The simpler it is implemented, the better. The ideal option would be to use a bot in a telegram, but for certain reasons it is impossible (it is not in the lock).
What are the possible alternatives to the bots in the telegram? Are there any other instant messengers that has clients for mobile platforms that allows you to implement such functionality?