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.

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:

  1. 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.
     
  2. 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) {
  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:

  1. 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;
  }
}

//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 : 

  1. 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
     
  2. 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;
  }
}

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"
}
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