Mempool SDK
Access Blocknative notification messages in Javascript with our simple web socket library
As Blocknative community members create SDKs in additional languages, we list them here. We greatly appreciate community member contributions.
Golang: https://github.com/bonedaddy/go-blocknative
These SDKs are not supported directly by Blocknative.
It should take less than 5 minutes to get going with the SDK.
Go to the Account page at https://explorer.blocknative.com/account and setup an account with an email address. You will receive an email to confirm your account.
You can read the Getting Started guide on the API Docs to get more information on how to set up an API Key for your purpose. API keys segment analytics data. Consider using different API keys for development, staging, and production releases.
npm install bnc-sdk
// For Node < v13 / CommonJS environments
const BlocknativeSdk = require('bnc-sdk');
const WebSocket = require('ws');
const Web3 = require('web3');
// OR
// For Node >= v13 / es module environments
import BlocknativeSdk from 'bnc-sdk'
import Web3 from 'web3'
import WebSocket from 'ws' // only neccessary in server environments
// create options object
const options = {
dappId: 'Your dappId here',
networkId: 1,
system: 'bitcoin', // optional, defaults to ethereum
transactionHandlers: [event => console.log(event.transaction)],
ws: WebSocket, // only neccessary in server environments
name: 'Instance name here', // optional, use when running multiple instances
onerror: (error) => {console.log(error)} //optional, use to catch errors
}
// initialize and connect to the api
const blocknative = new BlocknativeSdk(options)
Send a transaction using web3.js and get the transaction hash while its processing. Let the SDK know the hash and it will track its progress through the mempool and into a block.
// initialize web3
const web3 = new Web3(window.ethereum)
// get current account
const accounts = await web3.eth.getAccounts();
const address = accounts[0];
// create transaction options object
const txOptions = {
from: address,
to: "0x792ec62e6840bFcCEa00c669521F678CE1236705",
value: "1000000"
}
// initiate a transaction via web3.js
web3.eth.sendTransaction(txOptions).on('transactionHash', hash => {
// call with the transaction hash of the
// transaction that you would like to receive status updates for
const { emitter } = blocknative.transaction(hash)
// listen to some events
emitter.on('txPool', transaction => {
console.log(`Sending ${transaction.value} wei to ${transaction.to}`)
})
emitter.on('txConfirmed', transaction => {
console.log('Transaction is confirmed!')
})
// catch every other event that occurs and log it
emitter.on('all', transaction => {
console.log(`Transaction event: ${transaction.eventCode}`)
})
See how to get started with the SDK in this screencast:
SDK Quickstart Screencast
The following options object needs to be passed when initializing and connecting
type InitializationOptions = {
dappId?: string
networkId: number
system?: System
name?: string
appVersion?: string
transactionHandlers?: TransactionHandler[]
ws?: any
onopen?: () => void
ondown?: (closeEvent: CloseEvent) => void
onreopen?: () => void
onerror?: (error: SDKError) => void
onclose?: () => void
apiUrl?: string
}
Your unique API key that identifies your application. You can generate a
dappId by visiting the Blocknative account page and creating a free account. It is generally required, but is optional in the case of using the apiUrl parameter to pass the API key in as a query parameter.The system that you would like to monitor transactions on. Currently
ethereum is supported. Defaults to ethereum if no value is passed in.Valid Ethereum and EVM compatible network ids (use
ethereum for system):1Main Network5Goerli Test Network100xDai POA Network137Polygon Matic Mainnet Network
An array of functions that will each be called once for every status update for every transaction that is associated with this connection on a watched address or a watched transaction.
const handleTransactionEvent = event => {
const {
transaction, // transaction object
emitterResult // data that is returned from the transaction event listener defined on the emitter
} = event
console.log(transaction)
}
const options = {
// other options
transactionHandlers: [handleTransactionEvent]
}
If you are running the
sdk in a server environment, there won't be a native WebSocket instance available for the sdk to use, so you will need to pass one in. You can use any WebSocket library that you prefer as long as it correctly implements the WebSocket specifications. We recommend ws.If you are running multiple instances of the
sdk on the same client, passing in a name property allows the sdk to properly manage persistent state.A function that is called once the WebSocket has successfully connected to the Blocknative backend infrastructure.
A function that is called for every error that happens within the SDK including WebSocket connection errors. The function is called with an error object with the following parameters:
message : String - The error message, describing what went wrongerror : ErrorObject - An error object if ine exist (for instance a WebSocket error)transaction : String - The hash or txid passed to the call to transaction that caused the erroraccount : String - The address passed to the call to account that caused the error
If this function is not passed in then error will be thrown.
A function that is called when the WebSocket connection has dropped. The SDK will automatically reconnect.
A function that is called once the WebSocket has successfully re-connected after dropping.
A function that is called when the WebSocket has successfully been destroyed.
An optional (required if no
dappId provided) parameter that allows for the SDK to create a WebSocket connection to a url other than the default Blocknative WebSocket server. This can be useful in the case that you would like to use a WebSocket proxy server rather than including your API key client side.Import and initialize the SDK with the configuration options described above for client and server environments.
import BlocknativeSdk from 'bnc-sdk'
// create options object
const options = {
dappId: 'Your dappId here',
networkId: 1,
transactionHandlers: [event => console.log(event.transaction)],
onerror: (error) => {console.log(error)}
}
// initialize and connect to the api
const blocknative = new BlocknativeSdk(options)
// For Node < v13 / CommonJS environments
const BlocknativeSdk = require('bnc-sdk');
const WebSocket = require('ws');
// OR
// For Node >= v13 / es module environments
import BlocknativeSdk from 'bnc-sdk'
import WebSocket from 'ws' // only neccessary in server environments
// create options object
const options = {
dappId: 'Your dappId here',
networkId: 1,
transactionHandlers: [event => console.log(event.transaction)],
ws: WebSocket,
onerror: (error) => {console.log(error)}
}
// initialize and connect to the api
const blocknative = new BlocknativeSdk(options)
Now that your application is successfully connected via a WebSocket connection to the Blocknative back-end, you can register transactions to watch for updates (notifications). \
Once you have initiated a transaction and have received the transaction hash, you can pass it in to the
transaction function:// initiate a transaction via web3.js
web3.eth.sendTransaction(txOptions).on('transactionHash', hash => {
// call with the transaction hash of the transaction that you would like to receive status updates for
const {
emitter, // emitter object to listen for status updates
details // initial transaction details which are useful for internal tracking: hash, timestamp, eventCode
} = blocknative.transaction(hash)
})
The
emitter is used to listen for status updates. See the Emitter Section for details on how to use the emitter object to handle specific transaction state changes.The
details object contains the initial transaction details which are useful for internal tracking.If the library was initialized with transaction handlers, those handlers will also be called on each status change for the watched transaction.
If a transaction is watched that is currently in the txpool or was updated in the last 60 minutes, the SDK will immediately send a notification with the last detected status for that transaction.
If a watched transaction is replaced (status speedup or cancel), the SDK will automatically watch the hash of the replacement transaction for the client and start delivering notifications for it.
You can also register an account address to listen to any incoming and outgoing transactions that occur on that address using the
account method:// get the current accounts list of the user via web3.js
const accounts = await web3.eth.getAccounts()
// grab the primary account
const address = accounts[0]
// call with the address of the account that you would like to receive status updates for
const {
emitter, // emitter object to listen for status updates
details // initial account details which are useful for internal tracking: address
} = blocknative.account(address)
This will tell the Blocknative back-end to watch for any transactions that occur involving this address and any updates to the transaction status over time. The return object from successful calls to
account will include an event emitter that you can use to listen for those events and a details object which includes the address that is being watched.If you no longer want to receive notifications for an account address or transaction hash, you can use the
unsubscribe method:// unsubscribe from address
blocknative.unsubscribe(address)
// unsubscribe from Ethereum transaction hash
blocknative.unsubscribe(hash)
You may want to log an event that isn't associated with a transaction for analytics purposes. Events are collated and displayed in the developer portal and are segmented by your
dappId. To log an event, simple call event with a categoryCode and an eventCode, both of which can be any String that you like:blocknative.event({
categoryCode: String, // [REQUIRED] - The general category of the event
eventCode: String // [REQUIRED] - The specific event
})
The emitter object is returned from calls to
account and transaction and is used to listen to status updates via callbacks registered for specific event codes.// register a callback for a txPool event
emitter.on("txPool", transaction => {
console.log("Transaction is pending")
})
The first parameter is the
eventCode string of the event that you would like to register a callback for. For a list of the valid event codes, see the event codes section.The second parameter is the callback that you would like to register to handle that event and will be called with a transaction object that includes all of the relevant details for that transaction. See the Transaction Object section for more info on what is included.
Any data that is returned from the listener callback for
transaction emitters will be included in the object that the global transactionHandlers are called with under the emitterResult property.To prevent memory leaks on long running processes, you can use the
off method on the emitter to remove your callback listener:// remove callback for txPool event
emitter.off('txPool')
The callback that is registered for events on an emitter or included in the
transactionHandlers array will be called with the following transaction object:{
status: String, // current status of the transaction
hash: String,
to: String,
from: String,
gas: Number,
gasPrice: String,
gasPriceGwei: Number,
gasUsed: Number, // present on on-chain txns
nonce: Number,
value: String,
eventCode: String,
blockHash: String,
blockNumber: Number,
input: String,
baseFeePerGasGwei: number // option value
maxPriorityFeePerGasGwei: number// option value if transaction is of Type2
maxFeePerGasGwei: number // option value if transaction is of Type2
gasPriceGwei: number// option value
timeStamp: string // the UTC time of first detection of current status
dispatchTimeStamp: string // the UTC time of time of event dispatch
pendingTimeStamp: string // the UTC time of initial pending status detection
pendingBlockNumber: Number // the chain head block number at time of pending detection
transactionIndex: Number, // optional, present if status confirmed, failed
blockTimeStamp: String, // optional, present if status confirmed, failed - UTC time of miner block creation
counterParty: String, // address of the counterparty of the transaction when watching an account
direction: String, // the direction of the transaction in relation to the account that is being watched ("incoming" or "outgoing")
watchedAddress: String, // the address of the account being watched
timePending: String, // optional, present if status confirmed, failed, speedup, cancel. "-1" if first detection is on-chain.
blocksPending: Number, // optional, present if status confirmed, failed, speedup, cancel
originalHash: String, // if a speedup or cancel status, this will be the hash of the original transaction
asset: String, // the asset that was transfered
v: String,
r: String,
s: String,
contractCall: { // if transaction was a contract call otherwise undefined
contractAddress: String,
contractType: String,
methodName: String,
params: {
// params that the contract method was called with
},
contractName: String,
contractDecimals: Number (optional),
decimalValue: String (optional),
}
}
The SDK will send
confirmednotifications when a watchedAddress is detected in the internal transactions of a contract call. In this case, the confirmed transaction object will include details of the internal transactions and balance changes resulting from those internal transactions. Fields are not ordered."internalTransactions": [],
"netBalanceChanges": Object
Field | Description |
|---|---|
internalTransactions | Array of objects containing details of each internal transaction (see below) |
netBalanceChanges | Object containing details of balance changes for all addresses involved in internal transactions (see below) |
The
internalTransactions array contains details on each internal transaction executed by the contract call of the parent (main) transaction. Fields are not ordered."internalTransactions": [
{
"type": String,
"from": String,
"to": String,
"input": String,
"gas": Number,
"gasUsed": Number,
"value": String,
"contractCall": Object (optional, contains an additional param 'contractAlias' which will be the symbol of the token if this is an erc20 transfer or transferFrom)
},
...
]
Field | Description |
|---|---|
type | Type of internal transaction (one of CALL, DELEGATECALL, STATICCALL, CALLCODE) |
from | Address initiating the internal transaction call (typically the parent (main) transaction's contract address |
to | Address the internal transaction is calling or sending value to |
input | Data sent to internal transaction. For value transfers from external account initiating parent (main) transaction to another external account, this field contains 0x. For contract calls, this value contains the contract method signature and params as a hex string. |
gas | Maximum amount of gas available to the internal transaction |
gasUsed | Amount of gas actually used executing the internal transaction |
value | Amount of ETH transferred directly to to address from parent (main) transaction from address. |
contractCall | Optional. A series of keys and values specific to the contract method . This object is present only if the contract method call includes parameters and Blocknative decodes the internal transaction contract call (e.g. an ERC20 transfer). For details see decoded contract payload above.
NOTE: If the Internal transaction is an ERC20 transfer or transferFrom call, the contractCall object will include an additional field, contractAlias with the symbol of the token transferred. |
The
netBalanceChanges object contains details of all the balance changes resulting from the internal transactions details in the internalTransactions array."netBalanceChanges": {
"<address>": [
{
"delta": String,
"asset": {
"type": String,
"symbol": String
},
"breakdown": [
{
"counterparty": Atring,
"amount": String
}
]
}
],
...
}
Field | Description |
|---|---|
<address> | Address involved in internal transaction. Each address contains an array of balances changes, one for each counterparty |
asset | Details of the asset being transferred. Contains type and symbol. |
delta | Amount of value transfer (balance change) in wei to the <address>. Outgoing value is represented as a negative balance change and incoming value is represented as a positive balance change |
type | The type of asset transferred (e.g. "ether") |
symbol | The symbol of the asset transferred. "ETH" or appropriate ERC20 symbol |
breakdown | Array of individual transfers to <address> for the current asset |
counterparty | Address of the other side of the transfer relative to the <address> |
amount | The amount of asset transferred with this counterparty |
The following is a list of event codes that are valid, and the events that they represent:
all: Will be called for all events that are associated with that emitter. If a more specific listener exists for that event, then that will be called instead. This is useful to catch any remaining events that you haven't specified a handler fortxSent: Transaction has been sent to the networktxPool: Transaction was detected in the "pending" area of the mempool and is eligible for inclusion in a blocktxPoolSimulation: Transaction was detected in the "pending" area of the mempool and is eligible for inclusion in a block and has been simulated against the latest blocktxStuck: Transaction was detected in the "queued" area of the mempool and is not eligible for inclusion in a blocktxConfirmed: Transaction has been confirmedtxFailed: Transaction has failedtxSpeedUp: A new transaction has been submitted with the same nonce and a higher gas price, replacing the original transactiontxCancel: A new transaction has been submitted with the same nonce, a higher gas price, a value of zero and sent to an external address (not a contract)txDropped: Transaction was dropped from the mempool without being added to a block
You may want to filter events that occur on an Ethereum address and/or have the Blocknative server automatically decode the input data for a particular contract. To do this the
configuration function can be used to send a configuration that will be scoped globally or to a particular address:await blocknative.configuration({
scope: String, // [required] - either 'global' or valid Ethereum address
filters: Array, // [optional] - array of valid searchjs filter strings
abi: Array, // [optional] - valid contract ABI
watchAddress: Boolean // [optional] - Whether the server should automatically watch the "scope" value if it is an address
})
// returns a promise that resolves once the configuration has been applied
// or rejects if there was a problem with the configuration
There is a limit of 50 configurations per connection / API key. If you need to watch more than 50 addresses and also filter them, it is recommended that you use the
blocknative.account method to subscribe to all of the addresses and then use the blocknative.configuration method to add a 'global' scoped filter that will apply to all of those addresses.scope - [required]The scope that the configuration will be applied to. Can be a
'global' configuration so that you can filter all events for all addresses that you are watching or a valid Ethereum address to scope the configuration to events that occur only on that address.filters - [optional]The filters that you would like applied to events in scope. The Blocknative server uses
jsql a JavaScript query language to filter events. Documentation for how to create filter queries can be found hereabi - [optional]A JavaScript ABI (application binary interface) so that the Blocknative server can automatically decode transaction input data
watchAddress - [optional]
If the
scope is an Ethereum address, then watchAddress can be set to true so that the Blocknative server can automatically watch the address in scope, rather than needing to send an extra call to blocknative.accountscope 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.Simulation platform provides visibility into the effects of internal transactions. It notably highlights
netBalanceChanges of the contract calls a pending transaction is making, based on the most current state of the chain. Check the Simulation Platform docs for detailed information.The SDK exposes a
multiSim method that can be used to simulate transactions over a current WebSocket connection. The multiSim method takes an array of transaction objects (can be an array of 1) that you would like to simulate against the next block.export interface Transaction {
from: string
to: string
value: number
gas: number
input: string
gasPrice?: number
maxPriorityFeePerGas?: number
maxFeePerGas?: number
}
const transactionsToSim = [
{
from: "0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B",
to: "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
gas: 332160,
gasPrice: 0,
input:
"0xfb3bdb4100000000000000000000000000000000000000000000003635c9adc5dea000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000746dff22206ce4e3da6d7eb4d537398be8f236d600000000000000000000000000000000000000000000000000000000624FD77D0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000094d916873b22c9c1b53695f1c002f78537b9b3b2",
value: 28981678599856504,
},
{
from: "0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B",
to: "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
gas: 332160,
gasPrice: 0,
input:
"0xfb3bdb4100000000000000000000000000000000000000000000003635c9adc5dea000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000746dff22206ce4e3da6d7eb4d537398be8f236d600000000000000000000000000000000000000000000000000000000624FD77D0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000094d916873b22c9c1b53695f1c002f78537b9b3b2",
value: 28981678599856504,
},
];
const result = await blocknative.multiSim(transactionsToSim)
console.log(result)
// {
// simulatedBlockNumber: 15016676,
// transactions: [
// {
// from: "0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B",
// to: "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
// value: 28981678599856504,
// gas: 332160,
// gasPrice: 0,
// input:
// "0xfb3bdb4100000000000000000000000000000000000000000000003635c9adc5dea000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000746dff22206ce4e3da6d7eb4d537398be8f236d600000000000000000000000000000000000000000000000000000000624FD77D0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000094d916873b22c9c1b53695f1c002f78537b9b3b2",
// type: 0,
// },
// {
// from: "0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B",
// to: "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
// value: 28981678599856504,
// gas: 332160,
// gasPrice: 0,
// input:
// "0xfb3bdb4100000000000000000000000000000000000000000000003635c9adc5dea000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000746dff22206ce4e3da6d7eb4d537398be8f236d600000000000000000000000000000000000000000000000000000000624FD77D0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000094d916873b22c9c1b53695f1c002f78537b9b3b2",
// type: 0,
// },
// ],
// gasUsed: 288832,
// internalTransactions: [[], []],
// netBalanceChanges: [[], []],
// error: ["execution reverted", "execution reverted"],
// simDetails: {
// blockNumber: 15016676,
// performanceProfile: {
// breakdown: [
// {
// label: "detected",
// timeStamp: "2022-06-24T05:18:52.555Z",
// },
// {
// label: "traceStart",
// timeStamp: "2022-06-24T05:18:52.558Z",
// },
// {
// label: "traceEnd",
// timeStamp: "2022-06-24T05:18:52.572Z",
// },
// {
// label: "dispatch",
// timeStamp: "2022-06-24T05:18:52.572Z",
// },
// ],
// },
// e2eMs: 17,
// },
// serverVersion: "0.137.0-0.1.0",
// system: "ethereum",
// network: "main",
// contractCall: [
// {
// status: "fulfilled",
// value: {
// methodName: "swapETHForExactTokens",
// params: {
// amountOut: "1000000000000000000000",
// deadline: "1649399677",
// path: [
// "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
// "0x94d916873b22c9c1b53695f1c002f78537b9b3b2",
// ],
// to: "0x746dff22206ce4e3da6d7eb4d537398be8f236d6",
// },
// contractAddress: "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
// contractType: "Uniswap V2: Router 2",
// },
// },
// {
// status: "fulfilled",
// value: {
// methodName: "swapETHForExactTokens",
// params: {
// amountOut: "1000000000000000000000",
// deadline: "1649399677",
// path: [
// "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
// "0x94d916873b22c9c1b53695f1c002f78537b9b3b2",
// ],
// to: "0x746dff22206ce4e3da6d7eb4d537398be8f236d6",
// },
// contractAddress: "0x7a250d5630b4cf539739df2c5dacb4c659f2488d",
// contractType: "Uniswap V2: Router 2",
// },
// },
// ],
// status: "simulated",
// eventCode: "txSimulation",
// timeStamp: "2022-06-24T05:18:50.157Z",
// };
You can download a Mempool Explorer configuration to be used with the SDK. You can also use your account page to download a configuration that was saved to a specific API key. Once you have the files (
configuration.json, sdk-setup.js) downloaded, drop them in to your project directory. They can then be imported and setup with the SDK:import BlocknativeSDK from 'bnc-sdk'
import configuration from './configuration'
import sdkSetup from './sdk-setup'
// function to handle all transaction events
function handleTransactionEvent(transaction) {
console.log('Transaction event:', transaction)
}
// initialize the SDK
const blocknative = BlocknativeSDK({
// ...other initialization options
transactionHandlers: [handleTransactionEvent]
})
// setup the configuration with the SDK
sdkSetup(blocknative, configuration)
Sign up for a free Blocknative Account at https://account.blocknative.com/ with your work email address.
Last modified 27d ago