Broadcasting a Message

Function

This API is used by an application to broadcast a message to all online devices that subscribe to a specified topic. After an application delivers a broadcast message to the platform, the platform returns a response to the application and then broadcasts the message to devices.

Note:

This API applies only to devices that use the MQTT protocol for access.

Debugging

You can debug this API through automatic authentication in API Explorer or use the SDK sample code generated by API Explorer.

URI

POST /v5/iot/{project_id}/broadcast-messages

**Table 1** Path Parameters
Parameter	Mandatory	Type	Description
project_id	Yes	String	Parameter description: project ID. For details about how to obtain the project ID, see Obtaining a Project ID.

Request Parameters

**Table 2** Request header parameters
Parameter	Mandatory	Type	Description
X-Auth-Token	No	String	Parameter description: user token. You can obtain the token by calling the IAM API Obtaining a User Token Through Password Authentication. In the returned response header, X-Subject-Token is the desired user token. For details about how to obtain the token, see Token Authentication.
Instance-Id	No	String	Parameter description: instance ID. Unique identifier of each instance in the physical multi-tenant scenario. Mandatory for professional editions and recommended in other cases. Log in to the IoTDA console and choose Overview in the navigation pane to view the instance ID. For details, see Viewing Instance Details.

**Table 3** Request body parameters
Parameter	Mandatory	Type	Description
app_id	No	String	Parameter description: resource space ID. This parameter is optional. If you have multiple resource spaces, you can use this parameter to specify the resource space to which the broadcast message belongs. If this parameter is not specified, the broadcast message will be sent to devices that subscribe the specified topic in the default resource space. Value: The value can contain a maximum of 36 characters. Only letters, digits, underscores (_), and hyphens (-) are allowed.
topic_full_name	Yes	String	Parameter description: (mandatory) complete name of the topic for receiving broadcast messages. To broadcast messages to devices, you can use this parameter to specify a complete topic name. Then, the IoT platform sends messages to all online devices that subscribe to the topic in the specified resource space. Broadcast topics do not need to be created on the console, but the topic prefix must be $oc/broadcast/.
message	Yes	String	Parameter description: content of the broadcast message. You need to encode the original message using Base64. The maximum length of the request body is 256 KB.
ttl	No	Integer	Parameter description: aging time of the caches of broadcasted messages on the platform, in minutes. The default value is 0, indicating that messages are not cached. The value of ttl must be a multiple of 5, that is, the granularity is 5 minutes. The maximum cache duration is 1,440 minutes. If this parameter is set to a value greater than 0, no more than 10 devices are allowed to subscribe to the same topic at the same time, or the API returns an error.
message_id	No	String	Parameter description: message ID, which is user-defined (UUID is recommended). If the value of ttl is greater than 0, the platform caches messages. You need to specify a unique value for message_id, or the API returns an error. Value: The value can contain a maximum of 128 characters. Only letters, digits, underscores (_), and hyphens (-) are allowed.

Response Parameters

Status code: 201

**Table 4** Response body parameters
Parameter	Type	Description
app_id	String	Parameter description: resource space ID.
topic_full_name	String	Parameter description: complete name of the topic for receiving broadcast messages.
message_id	String	Message ID, which is generated by the IoT platform to identify the message.
created_time	String	UTC time when the message was created. The value is in the format of yyyyMMdd'T'HHmmss'Z'.

Example Requests

Broadcasts a message.

POST https://{endpoint}/v5/iot/{project_id}/broadcast-messages

{
  "topic_full_name" : "$oc/broadcast/test",
  "message" : "SGVsbG9Xb3JsZA=="
}

Example Responses

Status code: 201

Created

{
  "app_id" : "jeQDJQZltU8iKgFFoW060F5SGZka",
  "topic_full_name" : "$oc/broadcast/test",
  "message_id" : "b1224afb-e9f0-4916-8220-b6bab568e888",
  "created_time" : "20151212T121212Z"
}