Function listenEvent

Subscribes to a custom event on the swarm bus service and executes a callback when the event is received.

This function sets up a listener for events with a specified topic on the swarm's bus service, invoking the provided callback with the event's payload when triggered. It is wrapped in beginContext for a clean execution environment, logs the operation if enabled, and enforces restrictions on reserved topic names (defined in DISALLOWED_EVENT_SOURCE_LIST). The callback is queued to ensure sequential processing of events. The function supports a wildcard client ID ("*") for listening to all clients or validates a specific client session. It returns an unsubscribe function to stop listening.

Throws

If the topicName is a reserved event source (e.g., "agent-bus"), or if the clientId is not "*" and no session exists.

Example

const unsubscribe = listenEvent("client-123", "custom-topic", (data) => console.log(data));
// Logs payload when "custom-topic" event is received for "client-123"
unsubscribe(); // Stops listening
  • listenEvent<T extends unknown = any>(
        clientId: string,
        topicName: string,
        fn: (data: T) => void,
    ): () => void

    Type Parameters

    • T extends unknown = any

      The type of the payload data, defaulting to any if unspecified.

    Parameters

    • clientId: string

      The ID of the client to listen for events from, or "*" to listen to all clients.

    • topicName: string

      The name of the event topic to subscribe to (must not be a reserved source).

    • fn: (data: T) => void

      The callback function to execute when the event is received, passed the event payload.

    Returns () => void

    A function to unsubscribe from the event listener.

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