Presence API for PubNub Windows C 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.

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 Windows C 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;

  pubnub_here_now(pn, chan, NULL);

  res = await(&amp;user_data);
  if (res == PNR_STARTED) {
    printf("pubnub_last_result() returned unexpected: PNR_STARTED(%d)\n", res);
    return -1;
  }

  if (PNR_OK == res) {
    puts("Here Now result:");
    msg = pubnub_get(pn);
    puts(msg);
  } else {
    printf("Here Now failed with code: %d\n", res);
    return -1;
  }

  return 0;
}

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

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 Windows C 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 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);
  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;

// Callback

int where_now(pubnub_t *pn) {
  char const *msg;
  enum pubnub_res res;

  pubnub_where_now(pn, "my_uuid");

  res = await(&amp;user_data);
  if (res == PNR_STARTED) {
    printf("pubnub_last_result() returned unexpected: PNR_STARTED(%d)\n", res);
    return -1;
  }

  if (PNR_OK == res) {
    puts("Where Now result:");
    msg = pubnub_get(pn);
    puts(msg);
  } else {
    printf("Where 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

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)

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

Get State :

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 of `channel group` names) to get the `state` for.
`uuid`	const char*	Optional	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"
}