Presence Basics
Presence gives you visibility into who is currently subscribed to a channel.
In other words, it monitors the subscribers of channels and delivers information on their real-time status. It also lets you:
- Measure channel occupancy.
- Monitor and add dynamic custom state information, like profile info, typing indicators, or current location.
- Use webhooks to have PubNub notify your server whenever presence events occur.
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.
When you have Presence enabled on your keyset in the Admin Portal, PubNub automatically creates additional presence equivalents of all channels. These presence channels are named after the main ones but contain an additional -pnpres
suffix. Their purpose is to track all presence events about users.
Get Online Users in Channel
When a client opens the app, it's often required to discover what other users are already subscribed to that channel (for example, to construct a chat room's online friends list). You can obtain a list of client User IDsUser ID
UTF-8 encoded, unique string of up to 64 characters used to identify a single client (end user, device, or server) that connects to PubNub.
Once the current state has been fetched, your app can rely on presence events to keep the user state up to date. Go to the Presence Events to learn more.
hereNow()
cache response time
hereNow()
cache response timeNote that hereNow()
has a 3 second response cache time.
- JavaScript
- Swift
- Objective-C
- Android
- C#
- Python
pubnub.hereNow(
{
channels: ["chats.room1", "chats.room2"],
includeState: true
},
function (status, response) {
console.log(status, response);
}
);
pubnub.hereNow(on: ["chats.room1", "chats.room2"]), and: [],
includeUUIDs: true, also: true { result in
switch result {
case let .success(response):
print("Successful hereNow Response: \(response)")
case let .failure(error):
print("Failed hereNow Response: \(error.localizedDescription)")
}
})
[self.pubnub hereNowForChannel: @[@"chats.room1", "chats.room2"]
withVerbosity:PNHereNowState
completion:^(PNPresenceChannelHereNowResult *result, PNErrorStatus *status) {
// parse the HereNow result parameter
}];
pubnub.hereNow()
.channels(Arrays.asList("chats.room1", "chats.room2"))
.includeState(true)
.async(new PNCallback<PNHereNowResult>() {
@Override
public void onResponse(PNHereNowResult result, PNStatus status) {
if (status.isError()) {
// handle error
return;
}
for (PNHereNowChannelData channelData : result.getChannels().values()) {
System.out.println("---");
System.out.println("channel:" + channelData.getChannelName());
System.out.println("occupancy: " + channelData.getOccupancy());
show all 24 linespubnub.HereNow()
.Channels(new string[] {"chats.room1", "chats.room2"})
.IncludeState(true)
.Execute(new PNHereNowResultEx((result, status) => {
if (status.Error) {
Console.WriteLine("HereNow error: " + status);
}
else if (result.Channels != null && result.Channels.Count > 0) {
foreach (KeyValuePair<string, PNHereNowChannelData> kvp in result.Channels) {
PNHereNowChannelData channelData = kvp.Value;
Console.WriteLine("---");
Console.WriteLine("channel:" + channelData.ChannelName);
Console.WriteLine("occupancy:" + channelData.Occupancy);
Console.WriteLine("Occupants:");
show all 27 linesdef here_now_callback(result, status):
if status.is_error():
print("here_now error: %s" % status)
return
for channel_data in result.channels:
print("---")
print("channel: %s" % channel_data.channel_name)
print("occupancy: %s" % channel_data.occupancy)
print("occupants: %s" % channel_data.channel_name)
for occupant in channel_data.occupants:
print("user_id: %s, state: %s" % (occupant.user_id, occupant.state))
show all 19 linesCustom user state
You can add custom state information to the users in your application. For more details, refer to Presence State.
Get Subscribed Channels for User
Sometimes it may be necessary for the client app to confirm the channels to which it's currently subscribed. Though this is rarely necessary to do this, except for possibly when you're testing and troubleshooting your app. This can be accomplished with the Where Now API.
- JavaScript
- Swift
- Objective-C
- Android
- C#
- Python
pubnub.whereNow({uuid: pubnub.uuid},
function (status, response) {
// handle status, response
}
);
pubnub.whereNow(for: pubnub.uuid) { result in
switch result {
case let .success(response):
print("Successful WhereNow Response: \(response)")
case let .failure(error):
print("Failed WhereNow Response: \(error.localizedDescription)")
}
}
[self.pubnub whereNowUUID:self.pubnub.uuid withCompletion:
^(PNPresenceWhereNowResult *result, PNErrorStatus *status) {
if (!status) {
NSLog(status);
}
else {
NSLog(result);
}
}];
pubnub.whereNow()
.async(new PNCallback<PNWhereNowResult>() {
@Override
public void onResponse(PNWhereNowResult result, PNStatus status) {
if (status.isError()) {
System.outprintln(status);
}
else {
System.outprintln(result);
}
}
});
pubnub.WhereNow()
.Execute(new PNWhereNowResultExt((result, status) => {
if (status.isError) {
Console.WriteLine(status.ErrorData.Information);
}
else {
Console.WriteLine(result);
}
}
));
envelope = pubnub.where_now().sync()
Presence events
Presence events are sent as users come online or go offline from the application. For more details on what they are and how you can receive these events directly from your client, refer to Presence Events.