How to make smart contract call using INFURA and NodeJS web3js

Question

I can not understand how I can prepare the transaction to be signed. Because INFURA does not support eth_sendTransaction but only eth_sendRawTransaction (INFURA API which then requires you to prepare a signed transaction) I have no idea how I can do that.

This is the code that I use to try send transaction, that it fails:

PrintProofOfWork.methods.printRequested(web3.utils.keccak256(gcodeHash)).send('0x' + serializedTransaction.toString('hex'))
        .then((result) => {
            log(`result of the invokation: ${result})`.red);
        }).catch((err) => {
        log(`error occurred: ${err})`.red);
    });

The error I get is:

error occurred: Error: Node error: {"code":-32601,"message":"The method eth_sendTransaction does not exist/is not available"})

Can anyone kindly show me how I can prepare a transaction that invokes the method of a Smart Contract with parameters, sign it and then send it with INFURA?

Answer 1

First of all INFURA does not allows to send unsigned transactions, so you have to sign them firstly and then pass them to INFURA.

To do this, you have to:

1. prepare the transaction
2. sign it
3. send it (using INFURA)

Please check INFURA documentation.

There is an example below:

const Web3 = require('web3')
const Tx = require('ethereumjs-tx')

// connect to Infura node
const web3 = new Web3(new Web3.providers.HttpProvider('https://mainnet.infura.io/INFURA_KEY'))

// the address that will send the test transaction
const addressFrom = '0x1889EF49cDBaad420EB4D6f04066CA4093088Bbd'
const privKey = 'PRIVATE_KEY'

// the destination address
const addressTo = '0x1463500476a3ADDa33ef1dF530063fE126203186'

// Signs the given transaction data and sends it. Abstracts some of the details 
// of buffering and serializing the transaction for web3.
function sendSigned(txData, cb) {
  const privateKey = new Buffer(config.privKey, 'hex')
  const transaction = new Tx(txData)
  transaction.sign(privateKey)
  const serializedTx = transaction.serialize().toString('hex')
  web3.eth.sendSignedTransaction('0x' + serializedTx, cb)
}

// get the number of transactions sent so far so we can create a fresh nonce
web3.eth.getTransactionCount(addressFrom).then(txCount => {

  // construct the transaction data
  const txData = {
    nonce: web3.utils.toHex(txCount),
    gasLimit: web3.utils.toHex(25000),
    gasPrice: web3.utils.toHex(10e9), // 10 Gwei
    to: addressTo,
    from: addressFrom,
    value: web3.utils.toHex(web3.utils.toWei(123, 'wei'))
  }

  // fire away!
  sendSigned(txData, function(err, result) {
    if (err) return console.log('error', err)
    console.log('sent', result)
  })

})