eth_subscribe - Optimism

Example code for the eth_subscribe json-rpc method. Сomplete guide on how to use eth_subscribe json-rpc in GetBlock.io Web3 documentation.

This method creates a subscription that pushes data to the client via WebSocket when events occur. Subscription types include 'newHeads' for new blocks, 'logs' for log events, 'newPendingTransactions' for pending transactions, and 'syncing' for sync status changes. This provides more efficient real-time updates compared to polling.

The eth_subscribe method creates a WebSocket subscription for real-time events on Optimism.

Parameters

Parameter	Type	Description	Required
subscriptionType	String	Type of subscription: 'newHeads', 'logs', 'newPendingTransactions', or 'syncing'.	Yes
filterObject	Object	(Optional, for 'logs') Filter object with address and topics.	No

Request

Javascript(ws)

import WebSocket from ('ws');

const webSocket = new WebSocket('wss://go.getblock.us/<ACCESS_TOKEN>');

async function subscribeToNewBlocks() {

  const request = {
    id: 1,
    jsonrpc: '2.0',
    method: 'eth_subscribe',
    params: ['newHeads'],
  };

  const onOpen = (event) => {
    webSocket.send(JSON.stringify(request));
  };

  const onMessage = (event) => {
    const response = JSON.parse(event.data);
    console.log(response);
  };

  try {
    webSocket.addEventListener('open', onOpen);
    webSocket.addEventListener('message', onMessage);
  } catch (error) {
    console.error(error);
  }
}

subscribeToNewBlocks();

WSCAT

Response

A successful response returns the following:

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x9ce59a13059e417087c02d3236a0b1cc"
}

Response Parameters

Field Name	Data Type	Description
subscription	string	The subscription ID
object	object	A block object containing the following fields:
object.number	string or null	The block number of the requested block, encoded as hexadecimal. null if the block is pending
object.hash	string or null	The block hash of the requested block. null if the block is pending
object.parenthash	string	Hash of the previous block used to generate the current block. Also known as the 'parent block'
object.nonce	string or null	The hash used to demonstrate proof-of-work. null if the block is pending. Returns 0x0000000000000000 when the consensus is proof-of-stake
object.sha3uncles	string	The hash of the list of uncles included in the block. Used to identify the block uniquely and to verify the integrity of the block's data
object.logsbloom	string or null	The bloom filter for the logs of the block, a data structure that allows for efficient membership testing of elements in a set (the logs included in the block). null if pending
object.transactionsroot	string	The root of the transaction trie of the block. Allows Arbitrum nodes to verify the integrity of the transactions in a block
object.stateroot	string	The root of the final state trie of the block. Included in the block header and used to verify the integrity of the state at the time the block was processed
object.receiptsroot	string	The root of the receipts trie of the block. A 32-byte hash of the root node of the receipts trie of all transactions in the block. Used to verify the integrity of the receipts data for all transactions
object.miner	string	The address of the miner receiving the reward
object.difficulty	string	A measure of how hard it is to find a valid block for the Arbitrum blockchain. A number that increases as more miners join the network and more blocks are added to the chain, encoded as hexadecimal
object.totaldifficulty	string	The cumulative sum of the difficulty of all blocks that have been mined in the Arbitrum network since the inception of the network. Measures the overall security and integrity of the Arbitrum network
object.extradata	string	Extra data included in a block by the miner who mined it. Often includes messages or other information related to the block
object.size	string	The size of this block in bytes as an integer value, encoded as hexadecimal
object.gaslimit	string	The maximum gas allowed in this block, encoded as hexadecimal
object.gasused	string	The total used gas by all transactions in this block, encoded as hexadecimal
object.timestamp	string	The Unix timestamp for when the block was collated
object.transactions	array	An array of transaction objects. See eth_getTransactionByHash for the exact shape
object.uncles	array	An array of uncle hashes

Use Case

The eth_subscribe method is commonly used for:

• Real-time block updates

• Live event streaming

• Efficient chain monitoring

• WebSocket applications

Error handling

Status Code	Error Message	Cause
404	Not found	Missing or invalid ACCESS_TOKEN.
-32601	notification not supported