Abstract: Disclosed herein are methods, systems, and apparatus, including computer programs encoded on computer storage media, for paying transportation fare. One of the methods includes: communicating to a toll terminal based on near field communication (NFC) technology, for paying a fare of using a transport system associated with the toll terminal; deducting, through a user account, the fare from an account balance associated with the user account; recording a remaining account balance associated with the user account after the fare is deducted; determining that the remaining account balance is less than a predetermined threshold; and providing the remaining account balance to a second mobile device over the NFC in response to determining that the remaining account balance is less than a predetermined threshold to trigger a request from the second mobile device to a transaction server to add balance to the user account.

Abstract: Disclosed herein are methods, systems, and apparatus, including computer programs encoded on computer storage media, for paying transportation fare. One of the methods includes: communicating to a toll terminal based on near field communication (NFC) technology, for paying a fare of using a transport system associated with the toll terminal; deducting, through a user account, the fare from an account balance associated with the user account; recording a remaining account balance associated with the user account after the fare is deducted; determining that the remaining account balance is less than a predetermined threshold; and providing the remaining account balance to a second mobile device over the NFC in response to determining that the remaining account balance is less than a predetermined threshold to trigger a request from the second mobile device to a transaction server to add balance to the user account.

Abstract: Methods, systems, and devices, including computer programs encoded on computer storage media, for monitoring a payment machine are provided. One of the methods includes: monitoring a payment machine's interaction with a terminal; and in response to determining that the payment machine is obtaining payment information from the terminal, sending, in a low-power-consumption communication mode, attribute information of the payment machine to the terminal, causing the terminal to send the attribute information to a server for monitoring an operation status of the payment machine.

Abstract: Methods, systems, and devices, including computer programs encoded on computer storage media, for monitoring a payment machine are provided. One of the methods includes: monitoring a payment machine's interaction with a terminal; and in response to determining that the payment machine is obtaining payment information from the terminal, sending, in a low-power-consumption communication mode, attribute information of the payment machine to the terminal, causing the terminal to send the attribute information to a server for monitoring an operation status of the payment machine.