Presence API for Mbed 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

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.

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 pubnub_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 mbed SDK:

enum pubnub_res pubnub_here_now (pubnub_t *p, const char *channel, const char *channel_group)

* required

Parameter	Description
p * Type: pubnub_t*	Pointer to PubNub client context.
channel Type: const char*	The string with the channel name (or comma-delimited list of channel names) to get presence info for.
channel_group Type: const char*	The string with the channel name (or comma-delimited list of channel group names) to get presence info for.

Basic Usage

Get a list of uuids subscribed to channel

// Sync

pubnub_here_now(
    ctx,
    "my_channel",
    NULL
);
pbresult = pubnub_await(ctx);
if (PNR_OK == pbresult) {
    char const *json_response = pubnub_get(ctx);
}

Rest Response from Server

The pubnub_here_now() function returns a list of uuid s 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']
}

Extended Here Now

Extended Here Now Options structure

Options for extended here now.

Method(s)

Declaration

struct pubnub_here_now_options { char const* channel_group; bool disable_uuids; bool state;};

Members

Member	Type	Description
channel_group	char const*	Channel group (a comma-delimited list of channel group names). If NULL, will not be used.
disable_uuids	bool	If true will not give uuids associated with occupancy.
state	bool	If true (and if disable_uuds is false), will give associated state alongside uuid info.

Initialize extended Here Now options

This returns the default options for here-now transactions. Will set channel_group = NULL, disable_uuids=true and state = false.

Method(s)

Declaration

struct pubnub_here_now_options pubnub_here_now_defopts(void);

Parameters

This method doesn't take any argument.

Basic Usage

struct pubnub_here_now_options opts = pubnub_here_now_defopts();

Returns

Type	Value	Description
struct pubnub_here_now_options		The default options for here-now.

Extended Here Now

The extended here now. It is basically the same as the pubnub_here_now(), just adding a few options that will be sent. Also, channel_group parameter is moved to options, it is not a regular function parameter, but, it's behavior is otherwise the same.

Method(s)

Declaration

enum pubnub_res pubnub_here_now_ex(pubnub_t *p, const char *channel, struct pubnub_here_now_options opt);

Parameters

* required

Parameter	Description
p Type: pubnub_t*	The Pubnub context.
channel Type: char const*	The string with the channel name (or comma-delimited list of channel names) to subscribe for.
opt Type: struct pubnub_here_now_options	Here-now options.

Basic Usage

struct pubnub_here_now_options opt = pubnub_here_now_defopts();
opt.state = 1;
pbresult = pubnub_here_now_ex(pn, "my_channel", opt);

Returns

Type	Value	Description
enum pubnub_res	PNR_STARTED	Success.
	other	Indicates the type of error.

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.

You can obtain information about the current list of channels to which a UUID is subscribed to by calling the pubnub_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 pubnub_where_now() you can use the following method(s) in the mbed SDK:

enum pubnub_res pubnub_where_now (pubnub_t *p, const char *uuid)

* required

Parameter	Description
p * Type: pubnub_t*	Pointer to PubNub client context.
uuid Type: const char*	The UUID of the user to get the channel presence. If NULL, the current UUID of the p context will be used.

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

char const *msg;
enum pubnub_res res;

res = pubnub_where_now(pn, "my_uuid");
if (res != PNR_STARTED) {
  printf("pubnub_where_now() returned unexpected: %d\n", res);
  return -1;
}

res = pubnub_await(pn);

if (res == PNR_STARTED) {
  printf("pubnub_await() returned unexpected: PNR_STARTED(%d)\n", res);

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Rest Response from Server

The pubnub_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

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

enum pubnub_res pubnub_set_state (pubnub_t *p, char const *channel, char const *channel_group, const char *uuid, char const *state)

* required

Parameter	Description
p * Type: pubnub_t*	Pointer to PubNub client context.
channel Type: char const*	The string with the channel name (or comma-delimited list of channel names) to set state for.
channel_group Type: char const*	The string with the channel name (or comma-delimited list of channel group names) to set state for.
uuid * Type: const char*	The UUID of the user for which to set state for. If NULL, the current UUID of the p context will be used.
state * Type: char const*	Has to be a JSON object

Get State

enum pubnub_res pubnub_state_get (pubnub_t *p, char const *channel, char const *channel_group, const char *uuid)

* required

Parameter	Description
p * Type: pubnub_t*	Pointer to Pubnub Client Context
channel Type: char const*	The string with the channel name (or comma-delimited list of channel names) to get the state for.
channel_group Type: char const*	The string with the channel name (or comma-delimited list of channel group names) to get the state for.
uuid Type: const char*	The UUID of the user for which to get the state for. If NULL, the current UUID of the p context will be used.

Basic Usage

Set State

pubnub_set_state(ctx, "hello_world", NULL, NULL, NULL);
pbresult = pubnub_await(ctx);
if (PNR_OK == pbresult) {
    printf("Set success\n");
}

Get State

pubnub_get_state(ctx, "my_channel", NULL, NULL);
pbresult = pubnub_await(ctx);
if (PNR_OK == pbresult) {
    char const *json_response = pubnub_get(ctx);
}

Returns

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

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