Blockchain as a Service:Subscribe to Events

This topic describes how to use WebSocket to receive events that occurred on a blockchain network.

API

GET /api/v1/networks/{network}/events/subscribe

URL path parameter	Description
network	The name of the channel.
access_token	The access token used to access the REST API.
source	The subscribed event type. The options include Tx, Config, Contract, and Block. If you subscribe to multiple types of events, separate the types with commas (,). “*“ indicates that all types of events are subscribed.

Message content

Parameter	Type	Description
id	String	The ID of an event, which is unique in the channel.
name	String	The name of an event.
type	EventType	The type of an event. The options include Tx, Config, Contract, and Block. Tx: transaction generation Config: system configuration changes of a blockchain Contract: smart contract setting events in transactions Block: block generation
network	String	The name of the channel.
instance_id	String	The instance ID of the subscribed event, which is unique in an organization.
content	Object	When EventType is set to Tx or Config, the value is in Transaction structure. When EventType is set to Contract, the value is of String type, and the event content is Base64-coded. When EventType is set to Block, the value is in Block structure.

Transaction

Parameter	Type	Description
id	String	The ID of a transaction. The value is empty when EventType is set to Config.
state	String	The state of a transaction. “VALID” indicates that the transaction is legal. Other values indicate that the transaction is illegal.
from	String	The transaction initiator, which is in the format of <Organization MSP>. <Username.>
to	String	The target chaincode called by the transaction. The value is empty when EventType is set to Config.
input	String	The chaincode calling parameter after JSON coding. When EventType is set to Config, the value is JSON-coded common.ConfigUpdate.
events	List<Event>	The blockchain event list generated by the transaction.
data	Object	Detailed content of the transaction. The data structure is common.Payload.

Block

Parameter	Type	Description
number	Integer	Height of a block.
hash	String	The hash value of the current block after Hex coding.
previous_hash	String	The hash value of the last block after Hex coding.
create_time	Integer	The creation time of the current block, which is a UNIX timestamp representing the number of milliseconds that have elapsed since the epoch time January 1, 1970, 00:00:00 UTC.
transactions	List<String>	The transaction ID list of the current block.

Examples

Sample request

wscat -c "ws://your.gateway.endpoint/api/v1/networks/channel3/events/subscribe?access_token=<Your URL Encoded Access Token>&source=%2A"

Sample of normal message pushing

{
  "type": "Block",
  "platform": "Fabric",
  "instance_id": "csi-e2ehmfqasth-bcw7tzao2dzeo",
  "network": "channel3",
  "id": "block-282",
  "name": "282",
  "content": {
    "number": 282,
    "hash": "f7b42d07509c463f8e8cde0fcc8325b42e8bf7fd6a7a24dd207eed297fcd6358",
    "create_time": 1581589504,
    "previous_hash": "b8de08d49217c1d8f4ea398c8c61fe2a5bc46ec7bb6c95f44dfd29eaf6c272ab",
    "transactions": [
      "dc90b701e27afa5120ee003ef9d51b86a2ff9e1a9d8537f65387bde6d92c5cba"
    ]
  }
}

Error codes

For more information, see Error codes.