DB2000, DB201x - service cable (COM)
DB2020 - USB cable or service cable (COM)
DB3150, DB3200, DB3210, DB3350 - USB cable
MSM7227, QSD8250 - ADB mode USB cable or TP mode recovery cable (COM)
QC8255/MSM7x30 - TP mode USB cable
All operations DONT require any activations or internet connection.
Firmware search and download requires server connection with 4SE firmware library. Once firmware is downloaded it can be used locally on user's PC without internet connection.