Presence API for PubNub POSIX C++ SDK
Presence enables you to track the online and offline status of users and devices in real time, as well as 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 Requires that the Presence add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-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.
Method(s)
To call Here Now
you can use the following method(s) in the Posix C++ SDK:
here_now (std::string const &channel, std::string const &channel_group="")
Parameter Type Required Description channel
std::string const & Yes Specifies channel
for which to return active uuids.channel_group
std::string const & Optional Specifies channel_group
for which to return active uuids.here_now (std::vector<std::string> const &channel, std::vector<std::string> const &channel_group)
Parameter Type Required Description channel
std::string const & Yes Specifies channel
vector for which to return active uuids.channel_group
std::string const & Yes Specifies 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) {
pn.here_now("my_channel").then([=](pubnub::context &pn, pubnub_res res) {
if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Here Now request failed" << std::endl;
}
});
}
// Functions
void on_here_now(pubnub::context &pn, pubnub_res res) {
if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Here Now request failed" << std::endl;
}
}
void here_now(pubnub::context &pn) {
pn.here_now("my_channel").then(on_here_now);
}
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 Requires that the Presence add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-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.
Note
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="")
Parameter Type Required Description uuid
std::string const & Yes Specifies 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;
}
}
//Lambdas
static void where_now(pubnub::context &ipn) {
ipn.where_now("my_uuid")
.then([=](pubnub::context &pn, pubnub_res res) {
if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Failed with code " << res << std::endl;
}
});
}
//Functions
static void on_where_now(pubnub::context &pn, pubnub_res res) {
if (PNR_OK == res) {
std::cout << pn.get() << std::endl;
} else {
std::cout << "Failed with code " << res << std::endl;
}
}
static void where_now(pubnub::context &ipn) {
ipn.where_now("my_uuid").then(on_where_now);
}
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 Requires that the Presence add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-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 (std::string const &channel, std::string const &channel_group, std::string const &uuid, std::string const &state)
Parameter Type Required Description channel
std::string const & Yes Channel
to set state onchannel_group
std::string const & Yes Channel_group
to set state onuuid
std::string const & Yes UUID
state
std::string const & Yes Serialized JSON state
state_get (std::string const &channel, std::string const &channel_group="", std::string const &uuid="")
Parameter Type Required Description channel
std::string const & Yes Channel
to get state.channel_group
std::string const & Optional Channel group
to get the state.uuid
std::string const & Optional UUID
Basic Usage
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;
}
}
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"
}