Presence API for PubNub POSIX C++ SDK

Presence enables you to track the online and offline status of users and devices in real time and store custom state information. Presence provides authoritative information on:

  • When a user has joined or left a channel
  • Who, and how many, users are subscribed to a particular channel
  • Which channel(s) an individual user is subscribed to
  • Associated state information for these users

Learn more about our Presence feature here.

Here Now

Requires Presence add-on

This method requires that the Presence add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

Description

You can obtain information about the current state of a channel including a list of unique user-ids currently subscribed to the channel and the total occupancy count of the channel by calling the here_now() function in your application.

Cache

This method has a 3 second response cache time.

Method(s)

To call Here Now you can use the following method(s) in the Posix C++ SDK:

Get a list of active UUIDs on a single channel

here_now (std::string const &channel, std::string const &channel_group="")
ParameterTypeRequiredDescription
channelstd::string const &YesSpecifies channel for which to return active uuids.
channel_groupstd::string const &OptionalSpecifies channel_group for which to return active uuids.

Get a list of active UUIDs on multiple channels

here_now (std::vector<std::string> const &channel, std::vector<std::string> const &channel_group)
ParameterTypeRequiredDescription
channelstd::string const &YesSpecifies channel vector for which to return active uuids.
channel_groupstd::string const &YesSpecifies channel_group vector for which to return active uuids.

Basic Usage

Get a list of uuids subscribed to channel

// Sync
void here_now(pubnub::context &pn) {
enum pubnub_res res;

res = pn.here_now("my_channel").await();

if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Here Now request failed" << std::endl;
}
}

// Lambdas
void here_now(pubnub::context &pn) {
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Rest Response from Server

The here_now() function returns a list of uuids currently subscribed to the channel.

  • uuids:["String","String", ... ,"String"] - List of UUIDs currently subscribed to the channel.
  • occupancy: Number - Total current occupancy of the channel.
{
occupancy : 4,
uuids : ['123123234t234f34fq3dq', '143r34f34t34fq34q34q3', '23f34d3f4rq34r34rq23q', 'w34tcw45t45tcw435tww3']
}

Where Now

Requires Presence add-on

This method requires that the Presence add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

Description

You can obtain information about the current list of channels to which a UUID is subscribed to by calling the where_now() function in your application.

Timeout events

If the app is killed/crashes and restarted (or the page containing the PubNub instance is refreshed on the browser) within the heartbeat window no timeout event is generated.

Method(s)

To call where_now() you can use the following method(s) in the Posix C++ SDK:

where_now (std::string const &uuid="")
ParameterTypeRequiredDescription
uuidstd::string const &YesSpecifies uuid for which current subscribed channels info is required

Basic Usage

You simply need to define the uuid and the callback function to be used to send the data to as in the example below.

Get a list of channels a UUID is subscribed to

//Sync
static void where_now(pubnub::context &pn) {
enum pubnub_res res;

try {
res = pn.where_now("my_uuid").await();

if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Failed with code " << res << std::endl;
}
} catch (std::exception &ex) {
std::cout << "Exception: " << ex.what() << std::endl;
}
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Rest Response from Server

The where_now() function returns a list of channels a uuid is subscribed to.

  • channels:["String","String", ... ,"String"] - List of channels a uuid is subscribed to.

Example Response

{
"channels": [
"lobby",
"game01",
"chat"
]
}

User State

Requires Presence add-on

This method requires that the Presence add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

Description

The state API is used to set/get key/value pairs specific to a subscriber uuid.

State information is supplied as a JSON object of key/value pairs.

Method(s)

Set State
set_state (std::string const &channel, std::string const &channel_group, std::string const &uuid, std::string const &state)
ParameterTypeRequiredDescription
channelstd::string const &YesChannel to set state on
channel_groupstd::string const &YesChannel_group to set state on
uuidstd::string const &YesUUID
statestd::string const &YesSerialized JSON state
Set State with Options
set_state (std::string const &channel, const &state, set_state_options options )
ParameterTypeRequiredDescription
channelstd::string const &YesChannel to set state on
statestd::string const &YesSerialized JSON state
optionsset_state_optionsYesExtra options for this call. Refer to the section below for more information.
set_state_options
ParameterTypeRequiredDescription
channel_groupstd::stringOptionalThe string with the channel name (or comma-delimited list of channel group names) to set state for.
user_idstd::stringYesThe user_id of the user for which to set state for. If NULL, the current user_id is used.
heartbeatboolYesIf set to true, you can set the state and make a heartbeat call at the same time via the /heartbeat endpoint.
Get State
state_get (std::string const &channel, std::string const &channel_group="", std::string const &uuid="")
ParameterTypeRequiredDescription
channelstd::string const &YesChannel to get state.
channel_groupstd::string const &OptionalChannel group to get the state.
uuidstd::string const &OptionalUUID

Basic Usage

Set State

static void set_state(pubnub::context &pn) {
enum pubnub_res res;

try {
std::string state("{\"first\":\"Robert\", \"last\":\"Plant\", \"age\":59, \"region\":\"UK\"}");
res = pn.set_state("my_channel", "", "my_uuid", state).await();

if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Failed with code " << res << std::endl;
}
} catch (std::exception &ex) {
std::cout << "Exception: " << ex.what() << std::endl;
}
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Set State with Heartbeat

std::cout << "Setting state with options" << std::endl;
if (PNR_OK == pb.set_state(
chan, "{\"x\":5}", pubnub::set_state_options().heartbeat(true)
).await()) {
std::cout << "State was set: " << pb.get() << std::endl;
}
else {
std::cout << "Setting state failed!" << std::endl;
}

Get State

static void get_state(pubnub::context &pn) {
enum pubnub_res res;

try {
res = pn.state_get("my_channel", "", "my_uuid").await();

if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Failed with code " << res << std::endl;
}
} catch (std::exception &ex) {
std::cout << "Exception: " << ex.what() << std::endl;
}
}

Returns

The state API returns a JSON object containing key value pairs.

{
first : "Robert",
last : "Plant",
age : 59,
region : "UK"
}

Heartbeat

Requires Presence add-on

This method requires that the Presence add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

Description

This method notifies channels and channel groups about a client's presence. You can send heartbeats to channels you are not subscribed to.

Method(s)

pb.heartbeat(std::string const& channel, std::string const& channel_group)
ParameterTypeRequiredDescription
channelstd::string const&OptionalThe string with the channel name (or comma-delimited list of channel names) to notify.
channel_groupstd::string const&OptionalThe string with the channel_group name (or comma-delimited list of channel group names) to notify.

Basic Usage

res = pb.heartbeat(chan, NULL).await();
if (PNR_OK == res) {
puts("Heartbeated! Got messages:");
}
else {
printf("Heartbeating failed with code: %d('%s')\n",
res,
pubnub_res_2_string(res));
}

Returns

This method returns a PubNub result enum or an error, depending on the status of the transaction.

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