​

Connection Request Handler

Using the connectionRequestHandler API method, you can intercept new peer connections and make decisions to accept or reject them based on the peer metadata set for a given device. (See Setting the Connection Request Handler)

Within the connectionRequestHandler you can use the connectionRequest parameter to access information about the peer connection request. (See Reading Connection Parameters)

• Peer key string — The identifier encoded as a string that uniquely identifies the requesting peer once discovered within the mesh.
• Connection type — The type of connection the peer is requesting.
• Peer metadata — The information provided by the end user associated with the peer making the request. (For more information on peer metadata, see Using Mesh Presence)

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Setting the Connection Request Handler

To accept or reject an incoming connection request:

ditto.presence.connectionRequestHandler = { connectionRequest in
    if (true) {
        return .allow
    } else {
        return .deny
    }
}

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Reading Connection Parameters

To see specific information associated with a requesting peer connection

ditto.presence.connectionRequestHandler = { connectionRequest in
    print(connectionRequest.peerKeyString)
    print(connectionRequest.connectionType)
    print(connectionRequest.peerMetadata)
    return .allow
}

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Sync Groups

By default, devices with the same app ID automatically form a mesh network to connect. However, you can streamline sync processes, minimize unnecessary data transfer, and optimize resource usage by configuring sync groups within your app.

For example, the following graphic illustrates two distinct restaurants identified by their location IDs: 7890 and 1234. When a peer establishes its identity with Ditto Server, it includes its location ID as part of the authentication callback.

Now, the two groups maintain isolated mesh networks:

A sync group is a collection of devices organized into a distinct group, allowing you to limit connections to specific subsets of devices rather than the default behavior of connecting all devices sharing the same app ID.

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Access Controls by Group

Sync groups are an optimization, not a security control — if a connection is created manually, such as by specifying a specific peer to connect to, then devices from different sync groups will still connect and sync as normal.

To enforce access controls by group, for instance, two groups of devices, each accessing different datasets, use Ditto’s permissions system. (See Data Authorization)

A device can only be in one sync group, which by default is group 0. Up to 2^32 distinct group numbers can be used in an app.

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Setting Up Sync Groups

To create a sync group:

ditto.transportConfig.global.syncGroup = 1234

do {
  try ditto.startSync()
} catch (let error) {
  print(error.localizedDescription)
}