Presence Basics
Presence monitors the subscribers of channels and delivers information on their real-time status.
It also lets you:
- Measure channel occupancy.
- Monitor dynamic custom state information, like profile info, typing notices, current location, or mood indicators.
- Use webhooks to have PubNub notify your server whenever presence events occur on any channel for your keys.
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. See how to enable Presence.
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 clients UUIDs, including clients' state data, and the total occupancy of the channel using the Here Now API.
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
Note that hereNow() has a 3 second response cache time.
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());
System.out.println("occupants:");
for (PNHereNowOccupantData occupant : channelData.getOccupants()) {
System.out.println("uuid: " + occupant.getUuid()
+ " state: " + occupant.getState());
}
}
}
});
pubnub.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:");
if (channelData.Occupants != null && channelData.Occupants.Count > 0) {
for (int index = 0; index < channelData.Occupants.Count; index++) {
PNHereNowOccupantData occupant = channelData.Occupants[index];
Console.WriteLine(string.Format("uuid: {0}", occupant.Uuid));
Console.WriteLine(string.Format("state:{1}", (occupant.State != null) ?
pubnub.JsonPluggableLibrary.SerializeToJsonString(occupant.State) : ""));
}
}
}
}
}
));
def 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("uuid: %s, state: %s" % (occupant.uuid, occupant.state))
pubnub.here_now()\
.channels("chats.room1", "chats.room2")\
.include_state(True)\
.pn_async(here_now_callback)
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.
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()