WebSocket API

Connect to the Blocknative service over WebSocket protocol

Creating a Socket Connection

A WebSocket connection should be created with the Blocknative service at wss://api.blocknative.com/v0. A successful connection will receive a response object that contains a status parameter with a value of 'ok'.

Required Parameters

The following parameters are required for all messages that are sent to the Blocknative service:

parameter

type

description

timeStamp

string

an ISO datetime string formatted YYYY-MM-DDThh:mm:ss.sTZD (see example for usage and https://www.w3.org/TR/NOTE-datetime for more details)

dappId

string

your API key

version

string

a version string usually used by the Blocknative SDK, but any version string can be used

blockchain

object

object specifying a the system and network of the blockchain (see next)

system

string

blockchain name, valid values are ethereum and bitcoin

network

string

blockchain network, valid values for support systems are:

Ethereum (and EVM compatible) - main, ropsten, rinkeby, goerli, kovan, xdai, bsc-main

Bitcoin - main, test

{
"timeStamp": "2021-01-11T06:21:40.197Z",
"dappId": "<YOUR_API_KEY>",
"version": "1",
"blockchain": {
"system": "ethereum"
"network": "main"
}
// ...rest of the message specific parameter
}

Initialization

Once a connection has been created with the Blocknative WebSocket service, an initialization message must be sent before any other messages so that the API key can be validated.

You API Key is created/managed from the Mempool Explorer account management page at https://explorer.blocknative.com/account. Note that API Key is called dappId in the Blocknative websocket protocol.

{
"categoryCode": "initialize",
"eventCode": "checkDappId",
// ...rest of the required parameters
}

Subscriptions

You can subscribe to receive transaction state change events by either watching a transaction hash/id or an address.

Ethereum Transaction Hash

// subscribe
{
"categoryCode": "activeTransaction",
"eventCode": "txSent",
"transaction": {
"hash": "0x0b4c94c414f71ddd5e7a625fcaa83ff1f93e9a7ca37e0f577b488ac8fd786655"
}
// ...rest of the required parameters
}
// unsubscribe
{
"categoryCode": "activeTransaction",
"eventCode": "unwatch",
"transaction": {
"hash": "0x0b4c94c414f71ddd5e7a625fcaa83ff1f93e9a7ca37e0f577b488ac8fd786655"
}
// ...rest of the required parameters
}

Bitcoin Transaction Id

// subscribe
{
"categoryCode": "activeTransaction",
"eventCode": "txSent",
"transaction": {
"txid": "edbd572eb93f54099c0c64781e5fb09b8b4d89f80229b1af3c293d3356ca9f71"
}
// ...rest of the required parameters
}
// unsubscribe
{
"categoryCode": "activeTransaction",
"eventCode": "unwatch",
"transaction": {
"txid": "edbd572eb93f54099c0c64781e5fb09b8b4d89f80229b1af3c293d3356ca9f71"
}
// ...rest of the required parameters
}

Address (Ethereum or Bitcoin)

// subscribe
{
"categoryCode": "accountAddress",
"eventCode": "watch",
"account": {
"address": "0xf5b5bd85157587771db6d49315b1712201569bdd"
}
// ...rest of the required parameters
}
// unsubscribe
{
"categoryCode": "accountAddress",
"eventCode": "unwatch",
"account": {
"address": "0xf5b5bd85157587771db6d49315b1712201569bdd"
}
// ...rest of the required parameters
}

Configurations

A configuration can be sent to the service to filter and/or decode transactions.

Transaction decoding is only available for Ethereum transactions

{
"categoryCode": "configs",
"eventCode": "put",
"config": {
"scope": "0xf5b5bd85157587771db6d49315b1712201569bdd",
"filters": [{"contractCall.methodName":"transfer"}],
"abi": [{
"constant": false,
"inputs": [{ "name": "newOwner", "type": "address" }],
"name": "setOwner",
"outputs": [],
"payable": false,
"stateMutability": "nonpayable",
"type": "function"
}],
"watchAddress": true
}
// ...rest of the required parameters
}

parameter

type

description

scope

string

A valid Ethereum address or 'global'

filters

string[]

An array of valid filters. The Blocknative service uses jsql, a JavaScript query language to filter events. Documentation for how to create filter queries can be found here

abi

string[]

A valid JSON ABI that will be used to decode input data for transactions that occur on the contract address defined in scope

watchAddress

boolean

defines whether the service should automatically watch the address as defined in scope

scope establishes the context in which a filter is applied. The global scope applies the filter to all transactions/addresses watched. Therefore a global scope only supports generic transaction elements. A scope set to an address can include filters, such as methodName,that are specific to the contract at that address. Similarly, the abi field only works for a contract specific scope.

Connection Drops

In the event of a WebSocket connection drop, no state is persisted between connections, so upon reconnection there will need to be logic defined that will:

  1. Send an initialization message

  2. Send all previously subscribed addresses, transactions and configs

Transaction Events

Each message sent to the service will receive an echo of that message back, this echo may be ignored for most purposes.

Every payload contains an eventCode parameter in the event object which indicates the type of event. Detailed documentation for event codes can be found in the here.

Ethereum Transaction Payload

{
"version":0,
"serverVersion":"0.85.8",
"timeStamp":"2021-01-06T01:25:24.716Z",
"connectionId":"49babf8c03a18ca8577b8dc42e4ab9e8cbdf3148d4b4b1e311f54f24c19e0e57",
"status":"ok",
"event":{
"timeStamp":"2021-01-06T01:25:24.716Z",
"categoryCode":"activeAddress",
"eventCode":"txConfirmed",
"dappId":"<DAPP ID>",
"blockchain":{
"system":"ethereum",
"network":"main"
},
"transaction":{
"status":"confirmed",
"monitorId":"GETH_1_F_PROD",
"monitorVersion":"0.77.3",
"timePending":"5482902",
"blocksPending":410,
"hash":"0x045fbad4090a25fc8267cf80f0f095a202cdac465d534e4c942b2068086e9aa3",
"from":"0xbA99926Be550865a956febAF4A747FFA0648797A",
"to":"0x111111125434b319222CdBf8C261674aDB56F3ae",
"value":"0",
"gas":324499,
"gasPrice":"61000000000",
"nonce":179,
"blockHash":"0x543bd57151cb7ab3024a18a459844790278861c712e9e4b58e1939a207e9fb82",
"blockNumber":11598068,
"transactionIndex":307,
"input": "0x34b0793b000000000000000...",
"gasUsed":"138022",
"asset":"ETH",
"watchedAddress":"0x111111125434b319222cdbf8c261674adb56f3ae",
"direction":"incoming",
"counterparty":"0xbA99926Be550865a956febAF4A747FFA0648797A"
}
}
}

Address subscription payload additional properties

If the transaction event is linked to an address subscription it will have the following properties that are unique to address subscriptions:

parameter

type

description

watchedAddress

string

the address subscription that this transaction is linked to, allowing you to match the transaction to a subscription

direction

string

a value of incoming or outgoing indicating whether the watched address is sending or receiving the transaction

counterparty

string

the counter-party to the watched address

Confirmed/failed transaction payload additional properties

Transactions with a status of confirmed will have the following additional properties that are not included in other statuses:

parameter

type

description

timePending

string

the time, in milliseconds, the transaction was pending before being included in a block

blocksPending

string

the number of blocks the transaction was pending before being included in a block

blockHash

string

the hash of the block containing the confirmed (or failed) transaction

blockNumber

number

the number of the block containing the confirmed (or failed) transaction

gasUsed

string

the amount of gas used to confirm (or fail) the transaction

Replaced transactions payload additional properties

Transactions that have been replaced and have a status of speedup or cancel will have the following additional properties that are not included in other statuses:

parameter

type

description

originalHash

string

the hash of the transaction that is being replaced

Bitcoin transaction payload

{
"version":0,
"serverVersion":"0.85.8",
"timeStamp":"2021-01-06T01:25:24.716Z",
"connectionId":"49babf8c03a18ca8577b8dc42e4ab9e8cbdf3148d4b4b1e311f54f24c19e0e57",
"status":"ok",
"event":{
"timeStamp":"2021-01-06T01:25:24.716Z",
"categoryCode":"activeAddress",
"eventCode":"txConfirmed",
"dappId":"<DAPP ID>",
"blockchain":{
"system":"ethereum",
"network":"main"
},
"transaction":{
txid: "5d7bab0b34eb623fb344264a9801c8655bbee85f7e55f2c6fcca813487d57164"
inputs: [
{address: "13kj3N13dhTLJcKfxs8KchbDN3pQBKcWLK", value: "0.0016"}
]
outputs: [
{address: "3LGrysb8jWcvdzQaZCVYoPbgJ1Puf2FmnJ", value: "0.0001524"},
{address: "1BABaiprMpm3Lmm3zuMhQs5gaGtjjguVBA", value: "0.00123649"}
],
netBalanceChanges: [
{address: "13kj3N13dhTLJcKfxs8KchbDN3pQBKcWLK", delta: "-0.0016"},
{address: "3LGrysb8jWcvdzQaZCVYoPbgJ1Puf2FmnJ", delta: "0.0001524"},
{address: "1BABaiprMpm3Lmm3zuMhQs5gaGtjjguVBA", delta: "0.00123649"}
]
fee: "0.00021111"
status: "confirmed",
system: "bitcoin",
network: "main",
timePending: "542538",
timeStamp: "2021-01-07T01:03:34.521Z",
txid: "5d7bab0b34eb623fb344264a9801c8655bbee85f7e55f2c6fcca813487d57164",
watchedAddress: "13kj3N13dhTLJcKfxs8KchbDN3pQBKcWLK",
rawTransaction: <RAW BITCOIN TRANSACTION>,
timePending: "542538",
blockHeight: "664885",
blockHash: "5d7bab0b34eb623fb344264a9801c8655bbee85f7e55f2c6fcca813487d57164",
}
}
}

Errors

Errors from the service are returned as messages with a status = 'error' and a reason string explaining the error.

Websocket payload is too large (60,000 bytes):

{
//...other params
status: 'error',
reason: 'message too large'
}

API key (dappId) parameter is missing:

{
//...other params
status: 'error',
reason: 'missing dappId'
}

API key (dappId) is invalid:

{
//...other params
status: 'error',
reason: '<DAPP-ID> is not a valid API key'
}

Attempt to watch an invalid address:

Address validity is based on the specific blockchain system used (bitcoin or ethereum).

{
//...other params
"status":"error",
"reason":"(string `address`) 0 is an invalid address in object `account` in object `websocket-event`"
}

Amount of messages has exceeded limit, see Rate Limits section below.

{
//...other params
status: 'error',
reason: 'ratelimit',
retryMs: 1000,
blockedMsg: <Message that was blocked>
}

Exceeded daily event limit for your API key, see Rate Limits section below.

{
//...other params
status: 'error',
reason: 'You have reached your event rate limit for today. See account.blocknative.com for details.'
}

IP has been rate limited, see Rate Limits section below.

{
//...other params
status: 'error',
reason: 'IP ratelimited**'**
}

Error received for using incorrect API version.

{
//...other params
status: 'error',
message: 'api version not supported',
}

Rate Limits

Daily per API key event rate limits that apply to Webhook events also apply to WebSocket events. Details on those limits can be found here.

The Blocknative service also limits how many messages can be sent over a duration of time, limiting to 50 messages per second.

A strategy that the Blocknative SDK uses to handle these limits is to create a message queue that processes messages and ensures that messages are spaced adequately. This can be especially important to implement when re-sending addresses to be subscribed after a connection dropout.

If a rate limit error message is received you can use the retryMs parameter to wait for that time period to continue sending messages. If a message was blocked due to a rate limit it will be included in the payload in the blockedMsg parameter so you can re-send that message after the retry delay, ensuring that no messages are dropped.