I'm developing an application that communicates with Arduino (Uno). I used two modes to communicate so far via USB (I used the libraries usb-serial-for-android and Physicaloid) and Bluetooth.
Sending and receiving data via Bluetooth was a bit slow and sometimes the information was simply not sent or received. In the communication via USB sending data was very fast, but even so, sometimes the connection does not open and is very random. I run the application and the USB connection does not open, I close the application, I run again and the connection opens. I have not tried connection via WIFI yet.
What is the ideal and safest way to connect to Arduino?