I would like to build an app in which a smartphone (using any OS) can discover other smartphones in the surroundings using Bluetooth. I know this can be probably achieved using BLE.
However, I would like a communication method, in which the devices can "ping" each other through Bluetooth by pressing a button within the app. The app should display something on both devices (like an image) for a few seconds if the buttons in both devices are pressed at the same time. For this, I assume BLE is not enough as it does not support communication between two smartphones and the BLE central and peripheral model does not seem to fit my goal.
I'm new to app development and while I found multiple questions on this, they are pretty old. Any thoughts on how this can be achieved.
Please give me pointers to libraries/resources which would help me achieve this.