eth-ws

Simple Eth RPC-JSON Websocket client

Get started

npm install eth-ws

const WsEth = require('eth-ws')
const wsEth = new WsEth('wss://mainnet.infura.io/ws/v3/YOUR-PROJECT-ID')

wsEth.call('eth_blockNumber')
  .then(blockNr => console.log(blockNr)) // parseInt(0x4b7) = 1207

Requests and responses are HEX encoded

Real-time Events

Supports PubSub subscriptions
https://geth.ethereum.org/docs/rpc/pubsub

wsEth.subscribe('newHeads')

// Gets executed on every new block
wsEth.on('newHeads', (block) => {
  console.log('New block:', parseInt(block.number))
})

Methods

https://eth.wiki/json-rpc/API#json-rpc-methods

const gasPrice = await wsEth.call('eth_gasPrice')
console.log(gasPrice/1e9, 'Gwei')

// or provide a callback to websocket `open` event
wsEth.on('open', async () => {
  console.log('WebSocket connection is now open!')
  const tx = await wsEth.call('eth_getTransactionByHash', TX_HASH)
  console.log(tx.from)
})

wsEth.on('error', err => console.error(err))

Signing and Sending transactions

// wsEth.setCommon({ chain: 'ropsten' })
const txData = {
  from: SENDER_ADDRESS
  to: RECEIVER_ADDRESS,
  gasPrice: '0x'+1e9.toString(16), // 1 Gwei
  value: '0x0', // 0
  nonce: await wsEth.call('eth_getTransactionCount', SENDER_ADDRESS, 'pending')
}
const rawTx = wsRpc.signTransaction(txData, PRIVATEKEY)

// Call returns a Promise combined with Event emitter

// 1) Using Promise for getting only the TransactionHash
const txHash = await wsEth.call('eth_sendRawTransaction', rawTransaction)
console.log('Transaction submitted:', txHash)

// 2) Using event emitter for TransactionHash and Receipt

// Can use .once to receive Receipt just once, otherwise gets emitted on every new block confirmation
wsEth.call('eth_sendRawTransaction', rawTransaction)
  .once('txHash', txHash => console.log('Transaction submitted': txHash))
  .once('receipt', ({error, receipt}) => {
    if (error) return console.error(error)
    
    const {status, gasUsed, transactionHash, blocksSince} = receipt

    if (parseInt(status) === 0) {
      console.log('Transaction was submitted and mined but failed')
    } else {
      console.log('Transaction was successful')
    }
    
    console.log(`Transaction was confirmed in ${blocksSince} blocks`)
    console.log('Gas used by tx:', gasUsed)
  })

Default block parameter

The following methods have an extra Default Block parameter:

• eth_getBalance
• eth_getCode
• eth_getTransactionCount
• eth_getStorageAt
• eth_call

latest | pending | earliest | Block nr HEX string

wsEth.call('eth_getTransactionCount', ADDRESS, 'pending')

For example, executing smart-contract functions on pending or past state of blockchain:

const abi = require('web3-eth-abi');
const contractABI = [{
    name: 'myMethod',
    type: 'function',
    inputs: [{
        type: 'uint256',
        name: 'myNumber'
    },{
        type: 'string',
        name: 'myString'
    }]
}]

// myMethod(2345675643, 'Hello!%')
const txParams = {
  to: CONTRACT_ADDRESS,
  from: SENDER_ADDRESS,
  data: abi.encodeFunctionCall(contractABI[0], ['2345675643', 'Hello!%']),
}

// pass defaultBlock - 'pending' or block number hex
wsEth.call('eth_estimateGas', txParams, 'pending')
  .then(gas => {
    console.log('Estimated gas required:', parseInt(gas))
    // "0x5208" -> 21000
  })
  .catch(err => {
    // for example 'execution reverted:'
    console.log(err.message)
  })

Signing on Custom Chains and Testnets

You can either

• pass the Chain common object to signTransaction
• or use setCommon to set it once for signing all future transactions

wsEth.setCommon({ chain: 'ropsten' })

wsEth.setCommon({ chain: 'ropsten', hardfork: 'byzantium' })

wsEth.setCommon({ chain: 'ropsten', hardfork: 'byzantium' })

wsEth.setCommon({
  customChain: {
    name: 'polygon-mainnet',
    chainId: 137,
    networkId: 137
  },
  baseChain: 'mainnet',
  hardfork: 'petersburg'
})