Presence API for PubNub 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 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 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)
ParameterTypeRequiredDescription
ppubnub_t*YesPointer to PubNub client context.
channelconst char*OptionalThe string with the channel name (or comma-delimited list of channel names) to get presence info for.
channel_groupconst char*OptionalThe 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

// Syncpubnub_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

Description

Options for extended here now.

Method(s)

Declaration

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

Members

MemberTypeDescription
channel_groupchar const*Channel group (a comma-delimited list of channel group names). If NULL, will not be used.
disable_uuidsboolIf true will not give uuids associated with occupancy.
stateboolIf true (and if disable_uuds is false), will give associated state alongside uuid info.

Initialize extended Here Now options

Description

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

TypeValueDescription
struct pubnub_here_now_optionsThe default options for here-now.

Extended Here Now

Description

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

ParameterTypeRequiredDescription
ppubnub_t*yesThe Pubnub context.
channelchar const*yesThe string with the channel name (or comma-delimited list of channel names) to subscribe for.
optstruct pubnub_here_now_optionsyesHere-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

TypeValueDescription
enum pubnub_resPNR_STARTEDSuccess.
otherIndicates the type of error.

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 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)
ParameterTypeRequiredDescription
ppubnub_t*YesPointer to PubNub client context.
uuidconst char*OptionalThe 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

// Syncchar 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 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

enum pubnub_res pubnub_set_state (pubnub_t *p, char const *channel, char const *channel_group, const char *uuid, char const *state)
ParameterTypeRequiredDescription
ppubnub_t*YesPointer to PubNub client context.
channelchar const*OptionalThe string with the channel name (or comma-delimited list of channel names) to set state for.
channel_groupchar const*OptionalThe string with the channel name (or comma-delimited list of channel group names) to set state for.
uuidconst char*YesThe UUID of the user for which to set state for. If NULL, the current UUID of the p context will be used.
statechar const*YesHas 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)
ParameterTypeRequiredDescription
ppubnub_t*YesPointer to Pubnub Client Context
channelchar const*OptionalThe string with the channel name (or comma-delimited list of channel names) to get the state for.
channel_groupchar const*OptionalThe string with the channel name (or comma-delimited list of channel group names) to get the state for.
uuidconst char*OptionalThe 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"}