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Tethering Target Message

The Tethering Target Continuity message is broadcast in order to elicit a response from a device to be used as a hotspot, which will reply with a Tethering Source message. In a typical usage example, a user clicks on the menu button that displays the list of available WiFi networks on a MacBook. This action generates a stream of Tethering Target messages that continue for the duration of the period in which the available networks tab is opened. In response, a hotspot-capable device linked to the same iCloud account (an iPhone or iPad with cellular connection) responds with Tethering Source messages to advertise its presence and connection capabilities, including battery status, type of cellular connection, and strength of cellular signal.

Tethering Target (Wi-Fi Settings Page) Message (btcommon.apple.type == 0x0d)

Field Name Info Example Length Type Notes
btcommon.apple.tethtgt.icloudid iCloud ID 67f36d01 4 Bytes Derived from user's iCloud DSID. Rotates every 24 hours. Constant across all devices on same iCloud Account

The message fields, observed values and their meaning:

  • Type: 1 byte, 0x0D -- indicates a Tethering Target message
  • Length: 1 byte, 0x04-- number of bytes in the message payload
  • Identifier: 4 bytes, variable -- An identifier tied to a user's Destination Signaling IDentifier (DSID) that rotates on a 24-hour cycle. This identifier can be used to track a user despite the use of random BD_ADDR.