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Auto-subscribe and broadcast messaging

· 2 min read
James Miller
James Miller

The latest Hotsock releases include automatic channel subscription on connect and broadcast messaging to unsubscribed channels, making it easier to build real-time applications with reduced client-side complexity.

Automatic channel subscriptions​

In Hotsock v1.7, you can now automatically subscribe to channels upon connection using the new autoSubscribe claim. This eliminates the need for a separate subscribe step when a connection always needs access to specific channels.

To automatically subscribe to a channel, set autoSubscribe to true in your channel claims when issuing a connect token:

{
  "exp": 1727107200,
  "scope": "connect",
  "channels": {
    "user.123": {
      "autoSubscribe": true
    }
  }
}

When the connection succeeds, the client will immediately receive a hotsock.subscribed message containing "autoSubscribed":true in its data payload, confirming the automatic subscription:

{
  "event": "hotsock.subscribed",
  "channel": "user.123",
  "data": { "autoSubscribed": true },
  "meta": { "uid": null, "umd": null }
}

This feature is particularly useful for:

  • User-specific channels where connections always need to receive messages for that user
  • Presence management where you need server-enforced presence detection immediately when clients connect
  • Reducing client complexity by eliminating the subscribe step for essential channels

Broadcasting to unsubscribed channels​

Hotsock v1.6 introduced the broadcast claim, which allows clients to send messages to channels without being subscribed. This is perfect for telemetry, logging, or fire-and-forget messaging scenarios, especially when combined with storing messages!.

To enable broadcast messaging, set the broadcast claim to true for the specific message events:

{
  "exp": 1727107200,
  "scope": "connect",
  "channels": {
    "user.123.usage": {
      "messages": {
        "client-stats": {
          "broadcast": true
        }
      }
    }
  }
}

With this configuration, clients can publish messages to the "user.123.usage" channel with the "client-stats" event without needing to subscribe to the channel first. This is supported for both WebSocket and client HTTP API messages.

Wrapping up​

Existing installations with auto-update enabled are already running v1.7 and have access to these features today. Other installations can be manually updated at any time. A full changelog is available with the complete list of changes included in these releases.