Presence API for PubNub C-Core 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
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.
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 C-Core 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 the channel name (or comma-delimited list of channel names) to get presence info for. |
channel_group | const char* | Optional | 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);
}
//callback
int here_now(pubnub_t *pn) {
char const *chan = "my_channel";
char const *msg;
enum pubnub_res res;
show all 34 linesRest Response from Server
The pubnub_here_now()
function returns a list of user_id 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
, global or not, doesn't matter.
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 arguments.
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
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
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.
You can obtain information about the current list of channels to which a user_id
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 C-Core SDK:
enum pubnub_res pubnub_where_now (
pubnub_t *p,
const char *user_id
)
Parameter | Type | Required | Description |
---|---|---|---|
p | pubnub_t* | Yes | Pointer to PubNub client context. |
user_id | const char* | Optional | The user_id of the user to get the channel presence. If NULL , the current user_id of the p context will be used. |
Basic Usage
You simply need to define the user_id
and the callback
function to be used to send the data to as in the example below.
Get a list of channels a USER_ID is subscribed to
// Sync
char const *msg;
enum pubnub_res res;
res = pubnub_where_now(pn, "my_user_id");
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);
show all 53 linesRest Response from Server
The pubnub_where_now()
function returns a list of channels a user_id
is subscribed to.
channels:["String","String", ... ,"String"]
- List of channels auser_id
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.
The state API is used to set/get key/value pairs specific to a subscriber user_id
.
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 *user_id,
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. |
user_id | const char* | Yes | The user_id of the user for which to set state for. If NULL , the current user_id of the p context will be used. |
state | char const* | Yes | 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 *user_id
)
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 of channel group names) to get the state for. |
user_id | const char* | Optional | The user_id of the user for which to get the state for. If NULL, the current user_id 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"
}
Extended Set 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.
Extended Set State Options structure
Parameter | Type | Required | Description |
---|---|---|---|
p | pubnub_t* | Yes | Pointer to PubNub client context. |
channel_group | char const* | Optional | The string with the channel name (or comma-delimited list of channel group names) to set state for. |
user_id | const char* | Yes | The user_id of the user for which to set state for. If NULL , the current user_id of the p context will be used. |
heartbeat | bool | Yes | If set to true , you can set the state and make a heartbeat call at the same time via the /heartbeat endpoint. |
Description
The extended state API is used to set/get key/value pairs specific to a subscriber user_id
with extra options.
State information is supplied as a JSON object of key/value pairs.
Method(s)
Set State with options
enum pubnub_res pubnub_set_state_ex(
pubnub_t* p,
const char* channel,
const char* state,
struct pubnub_set_state_options opts
)
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. |
state | char const* | Yes | Has to be a JSON object. |
opts | pubnub_set_state_options | Yes | Refer to Extended set state options structure. |
Basic Usage
Set State with Heartbeat
struct pubnub_set_state_options opt = pubnub_set_state_defopts();
opt.heartbeat = true;
pbresult = pubnub_set_state_ex(pn, "my_channel", "{}", opt);
Returns
The state API returns the result of the transaction.
State was set: {"status": 200, "message": "OK", "service": "Presence"}
Heartbeat
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.
This method notifies channels and channel groups about a client's presence. You can send heartbeats to channels you are not subscribed to.
Method(s)
enum pubnub_res pubnub_heartbeat(
pubnub_t* pb,
const char* channel,
const char* channel_group
)
Parameter | Type | Required | Description |
---|---|---|---|
pb | 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 notify. |
channel_group | char const* | Optional | The string with the channel_group name (or comma-delimited list of channel group names) to notify. |
Basic Usage
res = pubnub_heartbeat(pbp, chan, NULL);
if (PNR_STARTED == res) {
res = pubnub_await(pbp);
}
if (PNR_OK == res) {
puts("Heartbeated! Got messages:");
}
else {
printf("Heartbeating failed with code: %d('%s')\n",
res,
pubnub_res_2_string(res));
}
Returns
This method returns a PubNub result enum or an error, depending on the status of the transaction.