Presence Events

PubNub triggers presence events as users come online or go offline from the application.

Clients can receive these events directly or use webhooks to keep a user's online/offline status up to date. Use these events to keep track of active/inactive users and the total occupancy of the channel.

Presence webhooks

PubNub can invoke a REST endpoint on your server when presence events occur. For more information, refer to Presence Webhooks.

Presence Event Types

There are five main types of presence events:

Events	Description
join	Fires when a user subscribes to a channel.
leave	Fires when a user unsubscribes from a channel.
timeout	Fires when a connection to a channel is lost and the subscriber hasn't been seen in 300 seconds.
state-change	Fires anytime the user's state is changed.
interval	Fires in interval mode to provide an occupancy count and optionally include delta changes.

Add Presence Listeners

The Event listener and its handlers are briefly mentioned in the Application Setup section. Receiving the Presence events requires a Presence handler in the listener. Presence events will be received in this handler for all channels on which the client is subscribed and has enabled Presence events. In this handler, you have the following data available to you:

User ID / UUID

User ID is also referred to as UUID/uuid in some APIs and server responses but holds the value of the userId parameter you set during initialization.

Event Data	Description
action	The Presence event action type: join, leave, timeout, state-change, interval
channel	The channel on which the Presence action happened
occupancy	The total number of subscribers on the channel when the event occurred
uuid	The User ID of the client that published the message
timetoken	The timetoken when the Presence action took place (when PubNub published the event)
data	The state of the client that changed
subscription	The channel group or wildcard subscription pattern that the channel belongs to (if applicable)

JavaScript

pubnub.addListener({
  presence: function(event) {
    var action = event.action;
    var channelName = event.channel;
    var occupancy = event.occupancy;
    var eventTimetoken = event.timetoken;
    var occupantUserId = event.uuid;
    var state = event.state;
    var subscribeManager = event.subscription;
  }
});

Swift

let listener = SubscriptionListener()

// Add listener event callbacks
listener.didReceiveSubscription = { event in
  switch event {
    case presenceChanged(event):
      let action = event.action
      let channelName = event.channel
      let occupancy = event.occupancy
      let eventTimetoken = event.timetoken
      let occupantUserId = event.uuid
      let state = event.state
      let subscribeManager = event.subscription
  }
}

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Objective-C

- (void)pubnub:(PubNub *)pubnub didReceivePresenceEvent:(PNPresenceEventResult *)event {
  NSString *action = event.data.presenceEvent;
  NSString *channel = event.data.channel;
  NSString *occupantUserId = event.data.presence.uuid;
  NSString *eventTimetoken = event.data.presence.timetoken;
  NSInteger *occupancy = event.data.presence.occupancy;
  NSDictionary *state = event.data.presence.state;
}

Android

Reminder that SubscribeCallback is a Java Abstract class and requires that you implement all Abstract methods of the parent class. Below sample code is only showing one of the methods.

@Override
public void presence(PubNub pubnub, PNPresenceEventResult presence) {
  String action = presence.getEvent();
  String channel = presence.getChannel();
  String occupantUserId = presence.getUuid();
  String eventTimetoken = presence.getTimetoken();
  String occupancy = presence.getOccupancy();
  Object state = presence.getState();
}

C#

SubscribeCallbackExt subscribeCallback = new SubscribeCallbackExt(
  delegate (Pubnub pubnubObj, PNPresenceEventResult<object> event) {
    string action = event.GetEvent();
    string channel = event.GetChannel();
    string occupantUserId = event.GetPublisher();
    long eventTimetoken = event.GetTimetoken();
    int occupancy = event.GetOccupancy();
    object state = event.GetUserMetaData();
  }
);

pubnub.AddListener(subscribeCallback);

Python

class SubscribeHandler(SubscribeCallback):
  def presence(self, pubnub, event):
    action = event.event
    channel = event.channel
    occupantUserId = event.uuid
    eventTimetoken = event.timetoken
    occupancy = event.occupancy
    state = event.user_metadata

pubnub.add_listener(SubscribeHandler())

Subscribe to Presence Channel

Once you've added presence listeners, call subscribe with the withPresence flag enabled to receive presence events. Your client will now start receiving presence events in real time as users join and leave channels.

When you enable the withPresence flag, the SDK automatically subscribes you to presence channels. These channels are sister channels where presence events are published by PubNub. If you don't wish to subscribe to all presence channels in your list, you can subscribe to individual channels by appending pnpres to the channel name. For example, the presence channel for ch1 is ch1-pnpres.

JavaScript

pubnub.subscribe({
  channels: ["chats.room1", "chats.room2"],
  withPresence: true
});

Swift

pubnub.subscribe(
  to: ["chats.room1", "chats.room2"],
  withPresence: true
)

Objective-C

[self.pubnub subscribeToChannels: @[@"chats.room1", @"chats.room2"] withPresence:NO];

Android

pubnub.subscribe()
  .channels(Arrays.asList("chats.room1", "chats.room2"))
  .withPresence().execute();

C#

pubnub.Subscribe<string>()
  .Channels(new string[] {"chats.room1", "chats.room2"})
  .WithPresence()
  .Execute();

Python

pubnub.subscribe()\
  .channels("chats.room1", "chats.room2")\
  .with_presence()\
  .execute()

If you want to subscribe to a bunch of channels at once but you only want to listen for presence events on some of them, you'll invoke two separate subscribe requests.

JavaScript

// do listen for presence events for these channels
pubnub.subscribe({
  channels: ["chats.team1", "chats.dept5"],
  withPresence: true
});

// do not listen for presence events for these channels
pubnub.subscribe({channels: ["alerts.system", "alerts.team1"]});

Swift

// do listen for presence events for these channels
pubnub.subscribe(
  to: ["chats.team1", "chats.dept5"]
  withPresence: true
)

// do not listen for presence events for these channels
pubnub.subscribe(to: ["alerts.system", "alerts.team1"])

Objective-C

// do listen for presence events for these channels
[self.pubnub subscribeToChannels: @[@"chats.team1", @"chats.dept5"] withPresence:true];

// do not listen for presence events for these channels
[self.pubnub subscribeToChannels: @[@"chats.team1", @"chats.dept5"] withPresence:false];

Android

// do listen for presence events for these channels
pubnub.subscribe()
  .channels(Arrays.asList("chats.team1", "chats.dept5"))
  .withPresence();

// do not listen for presence events for these channels
pubnub.subscribe().channels(Arrays.asList("alerts.system", "alerts.team1"));

C#

// do listen for presence events for these channels
pubnub.Subscribe<string>()
  .Channels(new string[] {"chats.team1", "chats.dept5"})
  .WithPresence()
  .Execute();

// do not listen for presence events for these channels
pubnub.Subscribe<string>()
  .Channels(new string[] {"alerts.system", "alerts.team1"})
  .Execute();

Python

# do listen for presence events for these channels
pubnub.subscribe()\
  .channels("chats.team1", "chats.dept5")\
  .with_presence()\
  .execute()

# do not listen for presence events for these channels
pubnub.subscribe().channels("alerts.system", "alerts.team1").execute()

Presence Event Modes

The channel presence mode indicates when presence events are triggered for that channel. There are two modes: announce and interval. The mode is determined by the occupancy count (total actively subscribed clients on that channel) in relation to the Presence Announce Max setting on the Admin Portal.

This feature prevents high occupancy channels from becoming too noisy with presence events. If you require the announce mode to be in effect past 100 occupants, please contact PubNub Support.

Announce Mode

If the channel occupancy is less than the Announce Max setting (defaults to 20), the channel is in announce mode. In this mode, join, leave, timeout and state-change events are sent to subscribed clients as and when they're triggered.

User ID / UUID

User ID is also referred to as UUID/uuid in some APIs and server responses but holds the value of the userId parameter you set during initialization.

Join

{
  "action": "join",
  "channel": "chats.room1",
  "subscribedChannel": "chats.room1-pnpres",
  "timetoken": "15119466699655811",
  "occupancy": 2,
  "uuid": "user123",
  "timestamp": 1511946669
}

Leave

{
  "action": "leave",
  "channel": "chats.room1",
  "subscribedChannel": "chats.room1-pnpres",
  "timetoken": "15119466699655811",
  "occupancy": 2,
  "uuid": "user123",
  "timestamp": 1511946669
}

timeout

{
  "action": "timeout",
  "channel": "chats.room1",
  "subscribedChannel": "chats.room1-pnpres",
  "timetoken": "15119466699655811",
  "occupancy": 2,
  "uuid": "user123",
  "timestamp": 1511946669
}

State Change

{
  "action": "state-change",
  "channel": "room-1",
  "subscription": null,
  "actualChannel": null,
  "subscribedChannel": "room-1-pnpres",
  "state": {
    "mood": "grumpy"
  },
  "timetoken": "15119477895378127",
  "occupancy": 5,
  "uuid": "user1",
  "timestamp": 1511947789
}

Interval Mode

When a channel's occupancy exceeds the Announce Max setting, the channel goes into interval mode. In this mode, the join, leave, timeout events are replaced by an interval event which is sent every few seconds with the total occupancy on the channel. The Interval setting is also configurable for the settings page.

Triggering state-change events

The state-change events are always triggered regardless of which presence mode is active on a channel.

Presence Deltas

Additionally, you can enable the Presence Deltas setting from the Admin Portal. When this flag is enabled, interval events will also include a list of clients (User IDs) that joined, left or timed-out since the last interval event. The following is a simple representation of a Presence Delta event payload.

{
  "action": "interval",
  "channel": "chats.megachat",
  "occupancy": 27,
  "join": ["user123","user88"],
  "leave": ["user20", "user11", "user14"],
  "timeout": ["user42"],
  "subscribedChannel": "chats.megachat-pnpres",
  "timestamp": 1511947739,
  "timetoken": "15119477396210903"
}

If a Presence Delta payload exceeds 32KB, the here_now_refresh flag indicates that you should use the Here Now API if you wish to retrieve the list of client User IDs that may have triggered a join, leave or timeout since the last interval.