How Master and Slave concept works with Bluetooth?
Well, master/slave concept for Bluetooth resides on the protocol, not in the communications. On few words, this means Bluetooth Master is who has the ability to initiate connection with a peripheral (or slave), but onces connected both master and slave basically can interchange information without restriction (limited by application). If your bluetooth module or implementation has a SPP (serial port profile https://developer.bluetooth.org/TechnologyOverview/Pages/SPP.aspx) once the master finds and connect to the slave, information can flow in both ways like a chat (actually, chat application is the most common usage example of bluetooth modules)