Presence API for POSIX C++ SDK (legacy)

New SDK available

The POSIX C++ SDK is built on C-Core (legacy), which is still supported. If you are starting a new project, use the new C SDK.

Presence lets you track who is online or offline and store custom state information. Presence shows:

• When a user has joined or left a channel
• How many users are subscribed to a particular channel (occupancy)
• Which channels a user or device is subscribed to
• Presence state associated with these users

Learn more about our Presence feature in the Presence overview.

Here now

Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

This method returns information about the current state of a channel, including a list of unique user IDs (universally unique identifiers, UUIDs) currently subscribed to the channel and the total occupancy count of the channel.

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

1here_now (std::string const &channel, std::string const &channel_group="")

* required

channel* required#

type: Type: std::string const &

Specifies channel for which to return active uuids.

channel_group#

type: Type: std::string const &

Specifies channel_group for which to return active uuids. Wildcards are not supported.

Get a list of active UUIDs on multiple channels

1here_now (std::vector<std::string> const &channel, std::vector<std::string> const &channel_group)

* required

channel* required#

type: Type: std::string const &

Specifies channel vector for which to return active uuids.

channel_group* required#

type: Type: std::string const &

Specifies channel_group vector for which to return active uuids.

Sample code

Get a list of uuids subscribed to channel

1// Sync
2void here_now(pubnub::context &pn) {
3  enum pubnub_res res;
4

5  res = pn.here_now("my_channel").await();
6

7  if (PNR_OK == res) {
8    std::cout << pn.get() << std::endl;
9  } else {
10    std::cout << "Here Now request failed" << std::endl;
11  }
12}
13

14// Lambdas
15void here_now(pubnub::context &pn) {
16  pn.here_now("my_channel").then([=](pubnub::context &pn, pubnub_res res) {
17      if (PNR_OK == res) {
18        std::cout << pn.get() << std::endl;
19      } else {
20        std::cout << "Here Now request failed" << std::endl;
21      }
22    });
23}
24

25// Functions
26void on_here_now(pubnub::context &pn, pubnub_res res) {
27  if (PNR_OK == res) {
28    std::cout << pn.get() << std::endl;
29  } else {
30    std::cout << "Here Now request failed" << std::endl;
31  }
32}
33

34void here_now(pubnub::context &pn) {
35  pn.here_now("my_channel").then(on_here_now);
36}

show all 36 lines

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.

1{
2    occupancy : 4,
3    uuids : ['123123234t234f34fq3dq', '143r34f34t34fq34q34q3', '23f34d3f4rq34r34rq23q', 'w34tcw45t45tcw435tww3']
4}

Where now

Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

This method returns the list of channels a UUID is subscribed to.

Timeout events

If the app restarts (or the page refreshes) 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:

1where_now (std::string const &uuid="")

* required

uuid* required#

type: Type: std::string const &

Specifies uuid for which current subscribed channels info is required

Sample code

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

1//Sync
2static void where_now(pubnub::context &pn) {
3  enum pubnub_res res;
4

5  try {
6    res = pn.where_now("my_uuid").await();
7

8    if (PNR_OK == res) {
9      std::cout <<  pn.get() << std::endl;
10    } else {
11      std::cout << "Failed with code " << res << std::endl;
12    }
13  } catch (std::exception &ex) {
14    std::cout << "Exception: " << ex.what() << std::endl;
15  }
16}
17

18//Lambdas
19static void where_now(pubnub::context &ipn) {
20  ipn.where_now("my_uuid")
21    .then([=](pubnub::context &pn, pubnub_res res) {
22      if (PNR_OK == res) {
23        std::cout <<  pn.get() << std::endl;
24      } else {
25        std::cout << "Failed with code " << res << std::endl;
26      }
27  });
28}
29

30//Functions
31static void on_where_now(pubnub::context &pn, pubnub_res res) {
32  if (PNR_OK == res) {
33    std::cout <<  pn.get() << std::endl;
34  } else {
35    std::cout << "Failed with code " << res << std::endl;
36  }
37}
38

39static void where_now(pubnub::context &ipn) {
40  ipn.where_now("my_uuid").then(on_where_now);
41}

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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

1{
2    "channels": [
3        "lobby",
4        "game01",
5        "chat"
6    ]
7}

User state

Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

Clients can set a dynamic custom state (score, game state, location) for their users on one or more channels and store it on a channel as long as the user stays subscribed.

The state is not persisted, and when the client disconnects, the state data is lost. For more information, refer to Presence State.

Method(s)

Set state

1set_state (std::string const &channel, std::string const &channel_group, std::string const &uuid, std::string const &state)

* required

channel* required#

type: Type: std::string const &

Channel to set state on

channel_group* required#

type: Type: std::string const &

Channel_group to set state on

uuid* required#

type: Type: std::string const &

UUID

state* required#

type: Type: std::string const &

Serialized JSON state

Set state with options

1set_state (std::string const &channel, const &state, set_state_options options )

* required

channel* required#

type: Type: std::string const &

Channel to set state on

state* required#

type: Type: std::string const &

Serialized JSON state

options* required#

type: Type: set_state_options

Extra options for this call. Refer to the section below for more information.

set_state_options

* required

channel_group#

type: Type: std::string

The string with the channel name (or comma-delimited list of channel group names) to set state for.

user_id* required#

type: Type: std::string

The user_id of the user for which to set state for. If NULL, the current user_id is used.

heartbeat* required#

type: Type: bool

If set to true, you can set the state and make a heartbeat call at the same time via the /heartbeat endpoint.

Get state

1state_get (std::string const &channel, std::string const &channel_group="", std::string const &uuid="")

* required

channel* required#

type: Type: std::string const &

Channel to get state.

channel_group#

type: Type: std::string const &

Channel group to get the state.

uuid#

type: Type: std::string const &

UUID

Sample code

Set state

1static void set_state(pubnub::context &pn) {
2  enum pubnub_res res;
3

4  try {
5    std::string state("{\"first\":\"Robert\", \"last\":\"Plant\", \"age\":59, \"region\":\"UK\"}");
6    res = pn.set_state("my_channel", "", "my_uuid", state).await();
7

8    if (PNR_OK == res) {
9      std::cout <<  pn.get() << std::endl;
10    } else {
11      std::cout << "Failed with code " << res << std::endl;
12    }
13  } catch (std::exception &ex) {
14    std::cout << "Exception: " << ex.what() << std::endl;
15  }
16}

show all 16 lines

Set state with heartbeat

1std::cout << "Setting state with options" << std::endl;
2  if (PNR_OK ==  pb.set_state(
3      chan, "{\"x\":5}", pubnub::set_state_options().heartbeat(true)
4    ).await()) {
5      std::cout << "State was set: " << pb.get() << std::endl;
6    }
7    else {
8        std::cout << "Setting state failed!" << std::endl;
9    }

Get state

1static void get_state(pubnub::context &pn) {
2  enum pubnub_res res;
3

4  try {
5    res = pn.state_get("my_channel", "", "my_uuid").await();
6

7    if (PNR_OK == res) {
8      std::cout <<  pn.get() << std::endl;
9    } else {
10      std::cout << "Failed with code " << res << std::endl;
11    }
12  } catch (std::exception &ex) {
13    std::cout << "Exception: " << ex.what() << std::endl;
14  }
15}

Returns

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

1{
2    first   : "Robert",
3    last    : "Plant",
4    age     : 59,
5    region  : "UK"
6}

Heartbeat

Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

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)

1pb.heartbeat(std::string const& channel, std::string const& channel_group)

channel#

type: Type: std::string const&

The string with the channel name (or comma-delimited list of channel names) to notify.

channel_group#

type: Type: std::string const&

The string with the channel_group name (or comma-delimited list of channel group names) to notify.

Sample code

1res = pb.heartbeat(chan, NULL).await();
2if (PNR_OK == res) {
3    puts("Heartbeated! Got messages:");
4}
5else {
6    printf("Heartbeating failed with code: %d('%s')\n",
7            res,
8            pubnub_res_2_string(res));
9}

Returns

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