AnyCable

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Presence and whispering ​

Show who is online and share transient client-to-client events (typing indicators, cursor positions) with the JS SDK. Presence state lives in the AnyCable server, so there is no storage layer or heartbeat loop to write.

Server requirements: AnyCable v1.6+ with the broker enabled (anycable-go --presets=broker). See the server-side presence documentation.

Join the presence set ​

Joining is explicit: provide a unique user ID within the channel and arbitrary presence info:

js
import { createCable } from '@anycable/web'

const cable = createCable({ protocol: 'actioncable-v1-ext-json' })
const chatChannel = cable.streamFrom('room/42')

chatChannel.presence.join(user.id, { name: user.name })

Join once; the SDK re-joins automatically after every reconnection.

React to joins and leaves ​

js
chatChannel.on('presence', (ev) => {
  const { type, id, info } = ev

  if (type === 'join') {
    console.log('user joined', id, info)
  }

  if (type === 'leave') {
    // leave events carry only the id
    console.log('user left', id)
  }
})

The event type is one of join, leave, info (the full presence state), or error.

Read the current state ​

js
const users = await chatChannel.presence.info()

users //=> { 'user-1': { name: 'Alice' }, 'user-2': { name: 'Bob' } }

The first info() call performs a server request; after that, the SDK keeps the state up to date from join and leave events. Joining is optional for reading: a viewer can observe the presence set without appearing in it.

Leave ​

js
chatChannel.presence.leave()

Users also leave automatically on unsubscribe or disconnect. A client that disconnects without leaving stays in the presence set for the server's --presence_ttl (15 seconds by default), so a brief network interruption does not make the user appear offline.

Whisper client-to-client ​

Whispers are broadcasts published by clients and delivered to everyone else on the stream, bypassing your backend. They are transient: never stored, and clients that are offline miss them. Use them for typing indicators and live cursors; use regular broadcasts for anything that must be replayable.

js
// Publish
chatChannel.whisper({ event: 'typing', name: user.name })

// Receive (whispers arrive as regular messages on other clients)
chatChannel.on('message', (msg) => {
  if (msg.event === 'typing') {
    showTypingIndicator(msg.name)
  }
})

The sender does not receive its own whispers.

Enable whispering on the server

Public streams allow whispering out of the box. For signed streams, start the server with --streams_whisper (ANYCABLE_STREAMS_WHISPER=true). For Rails channels, mark the stream as whisperable: stream_from "room/42", whisper: true. See whispering docs.