Tethering Source Message

The Tethering Source Continuity message is broadcast in response to a Tethering Target message generated by another device (typically a MacBook) linked to the same iCloud account as the iPhone or iPad that is to be used as a hotspot. The Tethering Source message contains information pertaining to the battery life, and type and quality of cellular service the hotspot device has. Some of this information is listed in the "available WiFi networks" listed on the Tethering Target device when searching for the hotspot.

Tethering Source (Instant Hotspot) Message (btcommon.apple.type == 0x0e)

Field Name	Info	Example	Length	Type	Notes
btcommon.apple.tethsrc.version	Version	01	1	Bytes	Note sure what this pertains to
btcommon.apple.tethsrc.flags	Flags	00	1	Bytes	Note sure what these flags mean
btcommon.apple.tethsrc.battery	Battery Life (%)	87	1	UINT8
btcommon.apple.tethsrc.celltype	Cellular Connection Type	LTE (7)	2	UINT16
btcommon.apple.tethsrc.cellbars	Cell Service Quality (Bars)	5	1	UINT8

The message fields, observed values and their meaning:

• Type: 1 byte, 0x0E -- indicates a Tethering Source message
• Length: 1 byte, 0x06 -- number of bytes in the message payload
• Version: 1 byte, variable -- Not sure what this version pertains to
• Flags: 1 byte, variable -- Not sure what these flags mean
• Battery life: 1 byte, 0x0-0x64 -- Tethering Source battery percentage
• Cell service type: 2 bytes
  • 0 -- 4G (GSM)
  • 1 -- 1xRTT
  • 2 -- GPRS
  • 3 -- EDGE
  • 4 -- 3G (EV-DO)
  • 5 -- 3G
  • 6 -- 4G
  • 7 -- LTE
• Cellular service strength: 1 byte, 0-4 -- number of "bars" of cellular signal the Tethering Source currently has