Synchronization of Multiple iPhones

iOSDC2020 §

• How to connect and synchronize 20-30 devices simultaneously

  • Conditions: 20-30 devices, no internet required

• Idea 1: Core Bluetooth

  • Can create a network with a central node and multiple peripheral nodes
  • However, it can only support a maximum of 4-5 devices
    • It is possible to create a network on a tree structure to overcome this limitation, but it is too unstable and therefore not recommended.

• Idea 2: Multipeer Connectivity

  • Unlike Core Bluetooth,
    • Supports multiple connections (more devices)
    • Whether it uses Bluetooth or Wi-Fi is abstracted and not visible
  • A leader device needs to be designated
    • The device with the largest PeerID (randomly assigned) is chosen as the leader for convenience
  • The leader creates multiple sessions and connects to each child device
    • Why multiple sessions? It is recommended to keep the number of connections in Multipeer Connectivity to around 7-8.
  • If a new device has a larger PeerID than the current leader: a new session is started with the new device as the leader
  • If the leader device leaves: a new session is started with a new leader
  • These features allow for the creation of an organic network.

• However, there was a comment on NicoNico that said:

  • I have experienced significant lag when demonstrating MultiConnectivity at an exhibition venue…

• So caution is advised.