A method involves scanning a symbol presented on a point of sale (POS) system including a POS processor; decoding the symbol to obtain purchase data and bidirectional connection data, where the bidirectional connection data describes a bidirectional connection; generating payment data using the purchase data; establishing the bidirectional connection with the POS system; sending the payment data to the POS system over the bidirectional connection; and receiving payment confirmation from the POS system over the bidirectional connection in response to the sending the payment data.