Prepare for the PgBouncer and IPv4 deprecations on 26th January 2024

Realtime

Broadcast

Send and receive messages using Realtime Broadcast

Let's explore how to implement Realtime Broadcast to send messages between clients.

Usage

You can use the Supabase client libraries to send and receive Broadcast messages.

Initialize the client

Go to your Supabase project's API Settings and grab the URL and anon public API key.


_10
import { createClient } from '@supabase/supabase-js'
_10
_10
const SUPABASE_URL = 'https://<project>.supabase.co'
_10
const SUPABASE_KEY = '<your-anon-key>'
_10
_10
const client = createClient(SUPABASE_URL, SUPABASE_KEY)

Listening to broadcast messages

You can provide a callback for the broadcast channel to receive message. In this example we will receive any broadcast messages in room-1:


_16
// Join a room/topic. Can be anything except for 'realtime'.
_16
const channelA = clientA.channel('room-1')
_16
_16
// Simple function to log any messages we receive
_16
function messageReceived(payload) {
_16
console.log(payload)
_16
}
_16
_16
// Subscribe to the Channel
_16
channelA
_16
.on(
_16
'broadcast',
_16
{ event: 'test' },
_16
(payload) => messageReceived(payload)
_16
)
_16
.subscribe()

Sending broadcast messages

We can send Broadcast messages using channelB.send(). Let's set up another client to send messages.


_16
// Join a room/topic. Can be anything except for 'realtime'.
_16
const channelB = clientA.channel('room-1')
_16
_16
channelB.subscribe((status) => {
_16
// Wait for successful connection
_16
if (status !== 'SUBSCRIBED') {
_16
return null
_16
}
_16
_16
// Send a message once the client is subscribed
_16
channelB.send({
_16
type: 'broadcast',
_16
event: 'test',
_16
payload: { message: 'hello, world' },
_16
})
_16
})

Before sending messages we need to ensure the client is connected, which we have done within the subscribe() callback.

Broadcast options

You can pass configuration options while initializing the Supabase Client.

Self-send messages

By default, broadcast messages are only sent to other clients. You can broadcast messages back to the sender by setting Broadcast's self parameter to true.


_20
const myChannel = supabase.channel('room-2', {
_20
config: {
_20
broadcast: { self: true },
_20
},
_20
})
_20
_20
myChannel.on(
_20
'broadcast',
_20
{ event: 'test-my-messages' },
_20
(payload) => console.log(payload)
_20
)
_20
_20
myChannel.subscribe((status) => {
_20
if (status !== 'SUBSCRIBED') { return }
_20
channelC.send({
_20
type: 'broadcast',
_20
event: 'test-my-messages',
_20
payload: { message: 'talking to myself' },
_20
})
_20
})

Acknowledge messages

You can confirm that Realtime received your message by setting Broadcast's ack config to true.


_17
const myChannel = clientD.channel('room-3', {
_17
config: {
_17
broadcast: { ack: true },
_17
},
_17
})
_17
_17
myChannel.subscribe(async (status) => {
_17
if (status !== 'SUBSCRIBED') { return }
_17
_17
const serverResponse = await myChannel.send({
_17
type: 'broadcast',
_17
event: 'acknowledge',
_17
payload: {},
_17
})
_17
_17
console.log('serverResponse', serverResponse)
_17
})

Use this to guarantee that the server has received the message before resolving channelD.send's promise. If the ack config is not set to true when creating the channel, the promise returned by channelD.send will resolve immediately.

Send messages using REST calls

You can also send a Broadcast message by making an HTTP request to Realtime servers. This is useful when you want to send messages from your server or client without having to first establish a WebSocket connection.


_15
const channel = client.channel('test-channel')
_15
_15
// No need to subscribe to channel
_15
_15
channel
_15
.send({
_15
type: 'broadcast',
_15
event: 'test',
_15
payload: { message: 'Hi' },
_15
})
_15
.then((resp) => console.log(resp))
_15
_15
// Remember to clean up the channel
_15
_15
client.removeChannel(channel)