Publish/Subscribe API for FreeRTOS SDK (legacy)

New SDK available

The FreeRTOS SDK is built on C-Core (legacy), which is still supported. If you are starting a new project, use the new C SDK.

Publish

The pubnub_publish() function is used to send a message to all subscribers of a channel. To publish a message you must first specify a valid publish_key at initialization. A successfully published message is replicated across the PubNub Real-Time Network and sent simultaneously to all subscribed clients on a channel.

Messages in transit can be secured from potential eavesdroppers with SSL/TLS by setting ssl to true during initialization.

Publish anytime

It's not required to be subscribed to a channel in order to publish to that channel.

Message data

The message argument can contain any JSON serializable data, including: Objects, Arrays, Ints and Strings. data should not contain special FreeRTOS classes or functions as these will not serialize. String content can include any single-byte or multi-byte UTF-8 character.

JSON serialize

It is important to note that you should JSON serialize when sending signals/messages via PUBNUB.

Message size

The maximum number of characters per message is 32 KiB by default. The maximum message size is based on the final escaped character count, including the channel name. An ideal message size is under 1800 bytes which allows a message to be compressed and sent using single IP datagram (1.5 KiB) providing optimal network performance.

If the message you publish exceeds the configured size, you will receive the following message:

Message too large error

1["PUBLISHED",[0,"Message Too Large","13524237335750949"]]

To calculate payload size, use the message size calculator.

Need larger messages?

PubNub supports payloads larger than the standard limit, but raising it requires verifying compatibility with your use case.

Talk to our team to discuss increasing the message size limit for your use case.

Message publish rate

Messages can be published as fast as bandwidth conditions will allow. There is a soft limit based on max throughput since messages will be discarded if the subscriber can't keep pace with the publisher.

For example, if 200 messages are published simultaneously before a subscriber has had a chance to receive any messages, the subscriber may not receive the first 100 messages because the message queue has a limit of only 100 messages stored in memory.

Publishing to multiple channels

It is not possible to publish a message to multiple channels simultaneously. The message must be published to one channel at a time.

Publishing messages reliably

There are some best practices to ensure messages are delivered when publishing to a channel:

Publish to any given channel in a serial manner (not concurrently).
Check that the return code is success (for example, [1,"Sent","136074940..."])
Publish the next message only after receiving a success return code.
If a failure code is returned ([0,"blah","<timetoken>"]), retry the publish.
Avoid exceeding the in-memory queue's capacity of 100 messages. An overflow situation (aka missed messages) can occur if slow subscribers fail to keep up with the publish pace in a given period of time.
Throttle publish bursts in accordance with your app's latency needs, for example, Publish no faster than 5 msgs per second to any one channel.

Publishing compressed messages

Message compression lets you send the message payload as the compressed body of an HTTP POST call.

Every PubNub SDK supports sending messages using the publish() call in one or more of the following ways:

Uncompressed, using HTTP GET (message sent in the URI)
Uncompressed, using HTTP POST (message sent in the body)
Compressed, using HTTP POST (compressed message sent in the body)

This section outlines what compressing a message means, and how to use compressed messages to your advantage.

Compressed messages support

Currently, the C and Objective-C SDKs support compressed messages.

Message compression can be helpful if you want to send data exceeding the default 32 KiB message size limit, or use bandwidth more efficiently. Compressing messages is useful for scenarios that include high channel occupancy and quick exchange of information like ride hailing apps or multiplayer games.

Compression trade-offs

Small messages can expand - Compressed messages generally have a smaller size, and can be delivered faster, but only if the original message is over 1 KiB. If you compress a signal (whose size is limited to 64 bytes), the compressed payload exceeds the signal's initial uncompressed size.
CPU overhead can increase - While a smaller payload size is an advantage, working with compressed messages uses more CPU time than working with uncompressed messages. CPU time is required to compress the message on the sending client, and again to decompress the message on the receiving client. Efficient resource management is especially important on mobile devices, where increased usage affects battery life. Carefully consider the balance of lower bandwidth and higher speed versus any increased CPU usage.
Using Compression - Compression methods and support vary between SDKs. If the receiving SDK doesn't support the sender's compression method, or even if it doesn't support compression at all, the PubNub server automatically changes the compressed message's format so that it is understandable to the recipient. No action is necessary from you.

Messages are not compressed by default; you must always explicitly specify that you want to use message compression. Refer to the code below for an example of sending a compressed message.

1struct pubnub_publish_options opt = pubnub_publish_defopts();
2opt.method = pubnubSendViaPOSTwithGZIP;
3pbresult = pubnub_publish_ex(pn, "channel_name", "{\"message\":\"This message will be compressed\"}", opt);
4}]

Method(s)

To Publish a message you can use the following method(s) in the FreeRTOS SDK:

1enum pubnub_res pubnub_publish (pubnub_t *p, const char *channel, const char *message)

required

p required#: Type: pubnub_t*
Pointer to PubNub context. Can't be NULL
channel required#: Type: const char*
Pointer to string with the channel ID (or comma-delimited list of channel IDs) to publish to.
message required#: Type: const char*
Pointer to string containing message to publish in JSON format.

1enum pubnub_res pubnub_publishv2 (pubnub_t *p, const char *channel, const char *message, bool store_in_history, bool eat_after_reading)

required

p required#: Type: pubnub_t*
Pointer to Pubnub Client Context
channel required#: Type: const char*
Pointer to string with the channel ID (or comma-delimited list of channel IDs) to publish to.
message required#: Type: const char*
Pointer to string containing message to publish in JSON format.
store_in_history required#: Type: bool
If false, message will not be stored in history of the channel
eat_after_reading required#: Type: const char*
If true, message will not be stored for delayed or repeated retrieval or display

Sample code

Publish a message to a channel

1pubnub_t *ctx = pubnub_alloc();
2if (NULL == ctx) {
3    return -1;
4}
5pubnub_init(ctx, "demo", "demo");
6pubnub_publish(ctx, "hello_world", "\"Hello from Pubnub C-core docs!\"");
7pbresult = pubnub_await(ctx);
8if (pbresult != PNR_OK) {
9    pubnub_free(ctx);
10    return -1;
11}

Subscribe to the channel

Before running the above publish example, either using the Debug Console or in a separate script running in a separate terminal window, subscribe to the same channel that is being published to.

Rest response from server

The function returns the following formatted response:

1[1, "Sent", "13769558699541401"]

Other examples

Publish a JSON serialized message

1pubnub_t *ctx = pubnub_alloc();
2if (NULL == ctx) {
3    return -1;
4}
5pubnub_init(ctx, "demo", "demo");
6pubnub_publish(ctx, "hello_world", "{\"msg\": \"Hello from Pubnub C-core docs!\"}");
7pbresult = pubnub_await(ctx);
8if (pbresult != PNR_OK) {
9    pubnub_free(ctx);
10    return -1;
11}

Publish with cipher key

1res = pubnub_publish_encrypted(pbp, chan, "\"Hello world from crypto sync!\"", cipher_key);
2if (res != PNR_STARTED) {
3    printf("pubnub_publish() returned unexpected: %d\n", res);
4    pubnub_free(pbp);
5    return -1;
6}

Publish with cipher key using pubnub_publish_ex

Using this method you can reuse the cipherKey from the options.

1struct pubnub_publish_options opt = pubnub_publish_defopts();
2opt.cipher_key = my_cipher_key;
3pbresult = pubnub_publish_ex(pn, "my_channel", "42", opt);

Extended publish

Extended publish options structure

Holds all the options for extended publish.

Method(s)

Declaration

struct pubnub_publish_options { bool store; char const* cipher_key; bool replicate; char const* meta; enum pubnub_publish_method method; };

Members

Member	Type	Description
`store`	bool	If `true`, the message is stored in history. If `false`, the message is not stored in history.
`cipher_key`	char const*	If not `NULL`, the key used to encrypt the message before sending it to PubNub. Keep in mind that encryption is a CPU intensive task. Also, it uses more bandwidth, most of which comes from the fact that decrypted data is sent as `Base64` encoded `JSON` string. This means that the actual amount of data that can be sent as encrypted in a message is at least 25% smaller (than un-encrypted). Another point to be made is that it also does some memory management (allocating and deallocating).
`replicate`	bool	If `true`, the message is replicated, thus will be received by all subscribers. If `false`, the message is not replicated and will be delivered only to `Function` event handlers. Setting `false` here and `false` on `store` is referred to as a `Fire` (instead of a `publish`).
`meta`	char const*	An optional `JSON` object, used to send additional (`meta`) data about the message, which can be used for `stream filtering`.
`method`	enum pubnub_publish_method	Defines the method by which publish transaction will be performed. Can be `HTTP GET` or `POST`. If using `POST`, content can be `GZIP` compressed.

Initialize extended publish options

This returns the default options for publish V1 transactions. Will set:

Parameter
`store` Default: `true`
`cipher_key` Default: `NULL`
`replicate` Default: `true`
`meta` Default: `NULL`
`method` Default: `pubnubPublishViaGET`

Method(s)

Declaration

struct pubnub_publish_options pubnub_publish_defopts(void);

Parameters

This method doesn't take any argument.

Sample code

1struct pubnub_publish_options opts = pubnub_publish_defopts();

Returns

Type	Value	Description
struct `pubnub_publish_options`		The default options for `publish`.

Extended publish

The extended publish V1. Basically the same as pubnub_publish(), but with added optional parameters in @p opts.

Method(s)

Declaration

enum pubnub_res pubnub_publish_ex(pubnub_t *p, const char *channel, const char *message, struct pubnub_publish_options opts);

Parameters

required

p required#: Type: pubnub_t*
The Pubnub context.
channel required#: Type: char const*
The string with the channel ID to publish to.
message required#: Type: char const*
The message to publish. It needs to be JSON encoded.
opts required#: Type: struct pubnub_publish_options
The Publish options.

Sample code

1struct pubnub_publish_options opt = pubnub_publish_defopts();
2    opt.store = false;
3    pbresult = pubnub_publish_ex(pn, "my_channel", "42", opt);

Returns

Type	Value	Description
`enum pubnub_res`	PNR_STARTED	Success.
	other	Indicates the type of error.

Signal

Sends a signal @p message (in JSON format) on @p channel, using the @p pb context. This actually means "initiate a signal transaction".

It has similar behavior as publish, but unlike publish transaction, signal erases previous signal message on server (on a given channel,) and you can not send any metadata.

There can be only up to one signal message at the time. If it's not renewed by another signal, signal message disappears from channel history after a certain amount of time.

You can't (send a) signal if a transaction is in progress on @p pb context.

If transaction is not successful (@c PNR_PUBLISH_FAILED), you can get the string describing the reason for failure by calling pubnub_last_publish_result().

Keep in mind that the timetoken from the signal operation response is not parsed by the library, just relayed to the user. Only time-tokens from the subscribe operation are parsed by the library.

Also, for all error codes known at the time of this writing, the HTTP error will also be set, so the result of the PubNub operation will not be @c PNR_OK (but you will still be able to get the result code and the description).

By default, signals are limited to a message payload size of 64 bytes. This limit applies only to the payload, and not to the URI or headers. If you require a larger payload size, please contact support.

Method(s)

Declaration

enum pubnub_res pubnub_signal(pubnub_t* pb, char const* channel, char const* message);

Parameters

required

pb required#: Type: pubnub_t*
The Pubnub context in which to parse the response.
channel required#: Type: char const*
The string with the channel ID to signal to.
message required#: Type: char const*
The string with the signal, expected to be in JSON format.

Sample code

Signal a message to a channel

1enum pubnub_res = pubnub_signal(pb, "my_channel", "\"signalling\"");

Returns

Type	Value	Description
`enum pubnub_res`	PNR_OK	Transaction finished (signal sent).
	PNR_STARTED	Transaction started (started to send signal), will finish later.
	otherwise	Error, value indicates the reason for failure.

Message type enumeration (enum pubnub_message_type)

Defines the type of a message that is retrieved with subscribe V2:

Symbol	Value	Description
`pbsbPublished`	0	Published message (sent via Publish transaction)
`pbsbSignal`	1	A signal message (sent via Signal transaction)

This function causes the client to create an open TCP socket to the PubNub Real-Time Network and begin listening for messages on a specified channel ID. To subscribe to a channel ID the client must send the appropriate subscribe_key at initialization. By default a newly subscribed client will only receive messages published to the channel after the pubnub_subscribe() call completes.

Message retrieval

Typically, you will want two separate contexts for publish and subscribe. When changing the active set of subscribed channels, first call pubnub_leave() on the old set. The pubnub_subscribe() interface is essentially a transaction to start listening on the channel for arrival of next message. This has to be followed by pubnub_get()call to retrieve the actual message, once the subscribe transaction completes successfully. This needs to be performed every time it is desired to retrieve a message from the channel.

Unsubscribing from all channels

Unsubscribing from all channels, and then subscribing to a new channel Y is not the same as subscribing to channel Y and then unsubscribing from the previously-subscribed channel(s). Unsubscribing from all channels resets the last-received timetoken and thus, there could be some gaps in the subscription that may lead to message loss.

Method(s)

To Subscribe to a channel you can use the following method(s) in the FreeRTOS SDK:

1enum pubnub_res pubnub_subscribe (pubnub_t *p, const char *channel, const char *channel_group)

required

p required#: Type: pubnub_t*
Pointer to PubNub client context. Can't be NULL.
channel#: Type: const char*
The string with the channel ID (or comma-delimited list of channel IDs) to subscribe to.
channel_group#: Type: const char*
The string with the channel group name (or comma-delimited list of channel group names) to subscribe to.

Sample code

Subscribe to a channel:

1pubnub_t *ctx = pubnub_alloc();
2

3if (NULL == ctx) {
4    return -1;
5}
6pubnub_init(ctx, "demo", "demo");
7pubnub_subscribe(ctx, "hello_world", NULL);
8pbresult = pubnub_await(ctx);
9if (pbresult != PNR_OK) {
10    printf("Failed to subscribe, error %d\n", pbresult);
11    pubnub_free(ctx);
12    return -1;
13}
14else {
15    char const *msg = pubnub_get(ctx);
16    char const *channel = pubnub_get_channel(ctx);
17    while (msg != NULL) {
18        msg = pubnub_get(ctx);
19        channel = pubnub_get_channel(ctx);
20    }
21}
22pubnub_free(ctx);
show all 22 lines

Rest response from server

The output below demonstrates the response format to a successful call:

1[[], "Time Token"]

Other examples

Subscribing to multiple channels

It's possible to subscribe to more than one channel using the Multiplexing feature. The example shows how to do that using an array to specify the channel names.

Alternative subscription methods

You can also use Wildcard Subscribe and Channel Groups to subscribe to multiple channels at a time. To use these features, the Stream Controller add-on must be enabled on your keyset in the Admin Portal.

1pubnub_t *ctx = pubnub_alloc();
2if (NULL == ctx) {
3    return -1;
4}
5pubnub_init(ctx, "demo", "demo");
6pubnub_subscribe(ctx, "hello_world1,hello_world2,hello_world3", NULL);
7pbresult = pubnub_await(ctx);
8if (pbresult != PNR_OK) {
9    pubnub_free(ctx);
10    return -1;
11}
12else {
13    char const *msg = pubnub_get(ctx);
14    char const *channel = pubnub_get_channel(ctx);
15    while (msg != NULL) {
16        msg = pubnub_get(ctx);
17        channel = pubnub_get_channel(ctx);
18    }
19}
20pubnub_free(ctx);
show all 20 lines

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.

For any given channel there is an associated Presence channel. You can subscribe directly to the channel by appending -pnpres to the channel name. For example the channel named my_channel would have the presence channel named my_channel-pnpres.

1// Sync
2char *presence_channel = malloc(strlen(channel) + strlen(PUBNUB_PRESENCE_SUFFIX) + 1);
3strcpy(presence_channel, channel);
4strcat(presence_channel, PUBNUB_PRESENCE_SUFFIX);
5pubnub_subscribe(ctx, presence_channel, NULL);
6pbresult = pubnub_await(ctx);
7if (PNR_OK == pbresult) {
8    char const *presence_event = pubnub_get(ctx);
9    while (presnce_event != NULL) {
10        presence_event = pubnub_get(ctx);
11    }
12}
13

14// Callback
15void some_function(pubnub_t *ctx)
16{
17    char *presence_channel = malloc(strlen(channel) + strlen(PUBNUB_PRESENCE_SUFFIX) + 1);
18    strcpy(presence_channel, channel);
19    strcat(presence_channel, PUBNUB_PRESENCE_SUFFIX);
20    pubnub_subscribe(ctx, presence_channel, NULL);
21}
22

23void example_callback(pubnub_t *pb, enum pubnub_trans trans, enum pubnub_res result, void *user_data)
24{
25    if (PNR_OK == result) {
26        char const *presence_event = pubnub_get(pb);
27        while (presence_event != NULL) {
28            presence_event = pubnub_get(pb);
29        }
30    }
31}
show all 31 lines

Sample Responses

Join event

1{
2    "action": "join",
3    "timestamp": 1345546797,
4    "uuid": "175c2c67-b2a9-470d-8f4b-1db94f90e39e",
5    "occupancy": 2
6}

Leave event

1{
2    "action" : "leave",
3    "timestamp" : 1345549797,
4    "uuid" : "175c2c67-b2a9-470d-8f4b-1db94f90e39e",
5    "occupancy" : 1
6}

Timeout event

1{
2    "action": "timeout",
3    "timestamp": 1345549797,
4    "uuid": "76c2c571-9a2b-d074-b4f8-e93e09f49bd",
5    "occupancy": 0
6}

State change event

1{
  "action": "state-change",
  "uuid": "76c2c571-9a2b-d074-b4f8-e93e09f49bd",
  "timestamp": 1345549797,
  "data": {
      "isTyping": true
  }
8}

Interval event

1{
2    "action":"interval",
3    "timestamp":1474396578,
4    "occupancy":2
5}

When a channel is in interval mode with presence_deltas pnconfig flag enabled, the interval message may also include the following fields which contain an array of changed UUIDs since the last interval message.

joined
left
timedout

For example, this interval message indicates there were 2 new UUIDs that joined and 1 timed out UUID since the last interval:

1{
  "action" : "interval",
  "occupancy" : <# users in channel>,
  "timestamp" : <unix timestamp>,
  "joined" : ["uuid2", "uuid3"],
  "timedout" : ["uuid1"]
7}

If the full interval message is greater than 30 KB (since the max publish payload is ∼32 KiB), none of the extra fields will be present. Instead there will be a here_now_refresh boolean field set to true. This indicates to the user that they should do a hereNow request to get the complete list of users present in the channel.

1{
2    "action" : "interval",
3    "occupancy" : <# users in channel>,
4    "timestamp" : <unix timestamp>,
5    "here_now_refresh" : true
6}

Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. See Enable the features your app calls.

1// Sync
2enum pubnub_res res;
3

4for (;;) {
5  res = pubnub_subscribe(pn, NULL,  channel_group);
6  read_response(pn, res);
7}

Requires Stream Controller and Presence add-ons

This method requires both the Stream Controller and Presence add-ons are enabled for your key in the Admin Portal. See Enable the features your app calls.

1// Sync
2enum pubnub_res res;
3

4for (;;) {
5  res = pubnub_subscribe(pn, NULL, "family-pnpres");
6  read_response(pn, res);
7}

For subscribe, you don't use the cipher key at subscribe, but, when you get the received messages after the subscribe transaction has finished:

1char msg[MAX_MSG_LEN];
2pbresult = pubnub_get_decrypted(pn, my_cipher_key, s, sizeof s);
3if (PNR_OK == pbresult) {
4    /* Use the message in `msg` */
5}

or, for a different usability/safety trade-off:

1pubnub_bymebl_t msg = pubnub_get_decrypted_alloc(pn, my_cipher_key);
2if (msg.ptr != NULL) {
3    /* use the message in `msg.ptr` */
4    free(msg.ptr);
5}

Holds all the options for subscribe v2.

Method(s)

Declaration

struct pubnub_subscribe_v2_options {char const* channel_group;unsigned heartbeat;};

Members

Member	Type	Description
`channel_group`	char const*	Channel group (a comma-delimited list of channel group names). If `NULL`, will not be used.
`heartbeat`	unsigned	The channel activity timeout, in seconds. If below the minimum value supported by Pubnub, the minimum value will be used (instead).
`char const*`	filter_expr	The filter expression to apply. It's a predicate to apply to the metadata of a message. If it returns `true`, message will be received, otherwise, it will be skipped (as if not published). Syntax is not trivial, but can be described as mostly Javascript on the metadata (which is JSON, thus, "integrates well" with Javascript). For example, if your metadata is: `{"zec":3}`, then this filter `_would_ match` it: `zec==3`, while `zec==4` `would _not_`. If message doesn't have metadata, this will be ignored. If `NULL`, will not be used.

This returns the default options for subscribe transactions. Will set channel_group = NULL, heartbeat to default heartbeat value and filter_expr = NULL.

Method(s)

Declaration

struct pubnub_subscribe_v2_options pubnub_subscribe_v2_defopts(void);

Parameter

This method doesn't take any argument.

Sample code

1struct pubnub_subscribe_v2_options opts = pubnub_subscribe_v2_defopts();

Returns

Type	Value	Description
struct `pubnub_subscribe_options`		The default options for subscribe.

The V2 subscribe. To get messages for subscribe V2, use pubnub_get_v2() - keep in mind that it can provide you with channel and channel group info.

Method(s)

Declaration

enum pubnub_res pubnub_subscribe_v2(pubnub_t *p, const char *channel, struct pubnub_subscribe_v2_options opts);

Parameter

required

p required#: Type: pubnub_t*
The Pubnub context.
channel required#: Type: char const*
The string with the channel ID (or comma-delimited list of channel IDs) to subscribe for.
opts required#: Type: struct pubnub_subscribe_options
Subscribe V2 options.

Sample code

1struct pubnub_subscribe_v2_options opt = pubnub_subscribe_v2_defopts();
2opt.heartbeat = 412;
3pbresult = pubnub_subscribe_v2(pn, "my_channel", opt);

Returns

Type	Value	Description
`enum pubnub_res`	PNR_STARTED	Started.
	PNR_OK	Finished with a success (can only happen in the sync interface).
	other	Failed, Indicates the type of error.

V2 message structure

Pubnub V2 message has lots of data and here's how we express them for the pubnub_get_v2().

The "string fields" are expressed as Pascal strings, that is, a pointer with string length, and don't include a NUL character. Also, these pointers are actually pointing into the full received subscribe response, so, their lifetime is tied to the message lifetime and any subsequent transaction on the same context will invalidate them.

If a (string) field is not present, it will empty, meaning its size (length) will be zero and pointer (start) should be NULL (it might not be NULL, it's best to rely on size).

Method(s)

Declaration

struct pubnub_v2_message {char const* channel_group;unsigned heartbeat;};

Parameter

Member	Type	Description
`tt`	struct pubnub_char_mem_blok	The timetoken of the message - when it was published.
`region`	int	Region of the message - not interesting in most cases.
`flags`	int	Message flags (indicators).
`channel`	struct pubnub_char_mem_blok	Channel ID that message was published to.
`match_or_group`	struct pubnub_char_mem_blok	Subscription match or the channel group.
`payload`	struct pubnub_char_mem_blok	The message itself (its contents, payload).
`metadata`	struct pubnub_char_mem_blok	The message metadata, as published.
`message_type`	enum pubnub_message_type	The type of the message (`published`, `signal`).

Get V2 message

Parse and return the next V2 message, if any.

Do keep in mind that you can use pubnub_get() to get the full message array in JSON, but, then you'll have to parse it yourself, and pubnub_channel() and pubnub_channel_group() would not work. On the other hand, this function will fail if you use it on subscribe v1 response.

If there are no more messages, this will return a struct memset to zero. It's best to check if payload is empty, as there has to be a payload, while other fields/attributes are mostly optional.

Method(s)

Declaration

struct pubnub_v2_message pubnub_get_v2(pubnub_t* pbp);

Parameter

required

pbp required#: Type: pubnub_t*
The Pubnub context from which to get the next message.

Sample code

1struct pubnub_v2_message msg;
2for (msg = pubnub_get_v2(pbp); msg.payload.size > 0; msg = pubnub_get_v2(pbp)) {
3    puts("Received message:");
4    printf("  Channel    = '%.*s'\n", (int)msg.channel.size, msg.channel.ptr);
5    printf("  Timetoken  = '%.*s'\n", (int)msg.tt.size, msg.tt.ptr);
6    printf("  Metadata   = '%.*s'\n", (int)msg.metadata.size, msg.metadata.ptr);
7    printf("  Payload    = '%.*s'\n", (int)msg.payload.size, msg.payload.ptr);
8}

Returns

Type	Value	Description
`struct pubnub_v2_message`		The V2 message structure describing the next V2 message in the subscribe response. If there is no next message (response is empty, or subscribe V1, or some other transaction), the payload of the message will be empty.

Unsubscribe

To unsubscribe, you need to cancel a subscribe transaction.

If you configured SDK to be thread-safe, you can cancel at any time, but, the cancelling may actually fail - that is, your thread may wait for another thread to finish working with the context, and by the time your cancel request gets processed, the transaction may finish.
If you configured SDK to not be thread-safe, the only safe way to do it is to use the sync interface and:
1. Set the context to use non-blocking I/O.
2. Wait for the outcome in a loop, checking for pubnub_last_result() - rather than calling pubnub_await().
3. If a condition occurs that prompts you to unsubscribe, call pubnub_cancel().
4. Wait for the cancellation to finish (here you can call pubnub_await(), unless you want to do other stuff while you wait).

Unsubscribing from all channels

Method(s)

To Unsubscribe from a channel you can use the following method(s) in the FreeRTOS SDK:

required

p required#: Type: pubnub_t*
Pointer to Pubnub Client Context.

Sample code

Unsubscribe from a channel:

1pbresult = pubnub_subscribe(ctx, "my_channel", NULL);
2/* If we don't set non-blocking I/O, we can't get out of a blocked read */
3pubnub_set_non_blocking_io(ctx);
4/* Can't use pubnub_await() here, it will block */
5while (PNR_STARTED == pbresult) {
6    pbresult = pubnub_last_result(ctx);
7    /* Somehow decide we want to quit / unsubscribe */
8    if (should_stop()) {
9        pubnub_cancel(ctx);
10        /* If we don't have anything else to do, it's OK to await now,
11        but you could again have a loop "against" pubnub_last_result()
12        */
13        pbresult = pubnub_await(ctx);
14        break;
15    }
16}
17if (PNR_CANCELLED == pbresult) {
18    puts("Subscribe cancelled - unsubscribed!");
19}
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Rest response from server

The output below demonstrates the response to a successful call:

1{
2    "action" : "leave"
3}

Other examples

Unsubscribing from a channel group

1pbresult = pubnub_subscribe(ctx, NULL, "my_channel_group");
2/* If we don't set non-blocking I/O, we can't get out of a blocked read */
3pubnub_set_non_blocking_io(ctx);
4/* Can't use pubnub_await() here, it will block */
5while (PNR_STARTED == pbresult) {
6     pbresult = pubnub_last_result(ctx);
7     /* Somehow decide we want to quit / unsubscribe */
8     if (should_stop()) {
9         pubnub_cancel(ctx);
10         /* If we don't have anything else to do, it's OK to await now,
11          * but you could again have a loop "against" pubnub_last_result()
12          */
13         pbresult = pubnub_await(ctx);
14         break;
15     }
16}
17if (PNR_CANCELLED == pbresult) {
18    puts("Subscribe cancelled - unsubscribed!");
19}
show all 19 lines

New SDK available

Publish​

Publish anytime​

Message data​

JSON serialize

Message size​

Message too large error​

Need larger messages?

Message publish rate​

Publishing to multiple channels​

Publishing messages reliably​

Publishing compressed messages​

Compressed messages support

Compression trade-offs​

Method(s)​

Sample code​

Publish a message to a channel​

Subscribe to the channel

Rest response from server​

Other examples​

Publish a JSON serialized message​

Publish with cipher key​

Publish with cipher key using pubnub_publish_ex​

Extended publish​

Extended publish options structure​

Method(s)​

Declaration​

Members​

Initialize extended publish options​

Method(s)​

Declaration​

Parameters​

Sample code​

Returns​

Extended publish​

Method(s)​

Declaration​

Parameters​

Sample code​

Returns​

Signal​

Method(s)​

Declaration​

Parameters​

Sample code​

Signal a message to a channel​

Returns​

Message type enumeration (enum pubnub_message_type)​

Subscribe​

Message retrieval

Unsubscribing from all channels

Method(s)​

Sample code​

Rest response from server​

Other examples​

Subscribing to multiple channels​

Alternative subscription methods

Requires Presence

Sample Responses​

Join event​

Leave event​

Timeout event​

State change event​

Interval event​

Subscribe to a channel group​

Requires Stream Controller add-on

Subscribe to the Presence channel of a channel group​

Requires Stream Controller and Presence add-ons

Using cipherKey with subscribe​

Subscribe v2​

Subscribe v2 options structure​

Method(s)​

Declaration​

Members​

Initialize extended subscribe v2 options​

Method(s)​

Declaration​

Parameter​

Sample code​

Returns​

Publish

Publish anytime

Message data

Message size

Message too large error

Message publish rate

Publishing to multiple channels

Publishing messages reliably

Publishing compressed messages

Compression trade-offs

Method(s)

Sample code

Publish a message to a channel

Rest response from server

Other examples

Publish a JSON serialized message

Publish with cipher key

Publish with cipher key using pubnub_publish_ex

Extended publish

Extended publish options structure

Method(s)

Declaration

Members

Initialize extended publish options

Method(s)

Declaration

Parameters

Sample code

Returns

Extended publish

Method(s)

Declaration

Parameters

Sample code

Returns

Signal

Method(s)

Declaration

Parameters

Sample code

Signal a message to a channel

Returns

Message type enumeration (enum pubnub_message_type)

Subscribe

Method(s)

Sample code

Rest response from server

Other examples

Subscribing to multiple channels

Sample Responses

Join event

Leave event

Timeout event

State change event

Interval event

Subscribe to a channel group

Subscribe to the Presence channel of a channel group

Using cipherKey with subscribe

Subscribe v2

Subscribe v2 options structure

Method(s)

Declaration

Members

Initialize extended subscribe v2 options

Method(s)

Declaration

Parameter

Sample code

Returns

Subscribe v2

Method(s)

Declaration

Parameter

Sample code

Returns

V2 message structure

Method(s)

Declaration

Parameter

Get V2 message