Presence API for PubNub Mbed 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 pubnub_here_now()
function in your application.
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)
Parameter Type Required Description p
pubnub_t* Yes Pointer to PubNub client context. channel
const char* Optional The string
with thechannel
name (or comma-delimited list ofchannel
names) to getpresence
info for.channel_group
const char* Optional The string
with thechannel
name (or comma-delimited list of channelgroup
names) to getpresence
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
Description
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). IfNULL
, will not be used.disable_uuids
bool If true
will not give uuids associated with occupancy.state
bool If true
(and ifdisable_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
Type | Value | Description |
---|---|---|
struct pubnub_here_now_options | The 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
Parameter Type Required Description p
pubnub_t* yes The Pubnub context. channel
char const* yes The string with the channel
name (or comma-delimited list of channel names) to subscribe for.opt
struct pubnub_here_now_options yes 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 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 pubnub_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 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)
Parameter Type Required Description p
pubnub_t* Yes Pointer to PubNub client context. uuid
const char* Optional The UUID
of the user to get thechannel
presence. IfNULL
, the currentUUID
of thep
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);
return -1;
}
if (PNR_OK == res) {
puts("Were Now result:");
msg = pubnub_get(pn);
puts(msg);
} else {
printf("Were Now failed with code: %d\n", res);
return -1;
}
return 0;
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 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)
enum pubnub_res pubnub_set_state (pubnub_t *p, char const *channel, char const *channel_group, const char *uuid, char const *state)
Parameter | Type | Required | Description |
---|---|---|---|
p | pubnub_t* | Yes | Pointer to PubNub client context. |
channel | char const* | Optional | The string with the channel name (or comma-delimited list of channel names) to set state for. |
channel_group | char const* | Optional | The string with the channel name (or comma-delimited list of channel group names) to set state for. |
uuid | const char* | Yes | The UUID of the user for which to set state for. If NULL , the current UUID of the p context will be used. |
state | char const* | Yes | Has to be a JSON object |
enum pubnub_res pubnub_state_get (pubnub_t *p, char const *channel, char const *channel_group, const char *uuid)
Parameter Type Required Description p
pubnub_t* Yes Pointer to Pubnub Client Context channel
char const* Optional The string with the channel
name (or comma-delimited list of channel names) to get the state for.channel_group
char const* Optional The string with the channel
name (or comma-delimited list ofchannel group
names) to get thestate
for.uuid
const char* Optional The UUID
of the user for which to get thestate
for. If NULL, the currentUUID
of thep
context will be used.
Basic Usage
pubnub_set_state(ctx, "hello_world", NULL, NULL, NULL);
pbresult = pubnub_await(ctx);
if (PNR_OK == pbresult) {
printf("Set success\n");
}
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"
}