Presence API for FreeRTOS 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 FreeRTOS SDK:

enum pubnub_res pubnub_here_now (pubnub_t *p, const char *channel, const char *channel_group)
* required
ParameterDescription
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. Wildcards are not supported.

Sample code​

Get a list of uuids subscribed to channel​

// Sync
char const *chan = "my_channel";
char const *msg;
enum pubnub_res res;

res = pubnub_here_now(pn, chan, NULL);
if (res != PNR_STARTED) {
  return -1;
}

res = pubnub_await(pn);
if (res == PNR_STARTED) {
  return -1;
}

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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']
}

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 pubnub_where_now() you can use the following method(s) in the FreeRTOS SDK:

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

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​

// Sync

char const *msg;
enum pubnub_res res;

res = pubnub_where_now(pn, "my_uuid");
if (res != PNR_STARTED) {
  return -1;
}

res = pubnub_await(pn);
if (res == PNR_STARTED) {
  return -1;
}

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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
ParameterDescription
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
ParameterDescription
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.

Sample code​

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"
}
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