Send Transactions

In this section we're going to request testnet from a Ropsten faucet and then return testnet to a Ropsten faucet.

Whenever you create a transaction, you're writing data to the blockchain and updating its state. There are several ways to do this: sending ETH from one account to another, calling a smart contract function that writes data, and deploying a smart contract to the blockchain.

Every transaction on Ethereum must be signed using your private key to validate that is authorized by you.

Typically, MetaMask is used in dApp development as it securely holds your private keys in the browser and whenever the front end requires a signature it can call MetaMask. In this walkthrough, your MetaMask private key is stored in a secure .env file along with your endpoint.

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About eth_call Transactions

eth_call vs eth_sendRawTransaction

You can interact with contracts using eth_call or eth_sendRawTransaction. The table below compares the characteristics of both calls.

Essentially, you use eth_call to read data on the blockchain e.g. a balance. Use eth_sendRawTransaction when you are sending assets as in this walkthrough. This requires updating the state of the blockchain.

eth_call	eth_sendRawTransaction
Read-only	Write
Invokes contract function locally	Broadcasts to network
Does not change state of blockchain	Updates blockchain (for example, transfers ether between accounts)
Does not consume gas	Requires gas
Synchronous	Asynchronous
Returns value of contract function available immediately	Returns transaction hash only. Possible transaction may not be included in a block (for example, if the gas price is too low).

Useful Resources

Convert Wei to Gwei and ETH and vice versa

Get Started

Create a project

 
mkdir send-tx && cd send-tx

Install ethers.js library

Libraries simplify connecting an application to the Ethereum blockchain. You need to connect to Ethereum in order to read blockchain data and/or send transactions to the network.

 
npm install --save ethers

Request some Ropsten test ETH

We're going to be sending a transaction on the Ropsten network, so get hold of some Ropsten from the listed Ropsten faucets.
Make sure you configure your wallet to the Ankr Ropsten RPC Network to provide your address and to check your balance.
Check your wallet to see if it arrived.

Create a dotenv file

Install dotenv It is a good security practice to store environment variables such as API keys into a .env file and then use Dotenv to load them.

npm i dotenv

Create a .env file in your project folder

Add your MetaMask Account private key How?

ANKR_URL = "https://rpc.ankr.com/eth_ropsten/YOUR_API_KEY"
PRIVATE_KEY = "your-metamask-private-key"

Create a transaction.js file

async function main() {
  require('dotenv').config();
  const { ANKR_URL, PRIVATE_KEY } = process.env;

  const Web3 = require('web3')
  const web3 = new Web3(ANKR_URL)
 
  const myAddress = '0x1701A33B1f8E9F934Dccff20A1AfcaD9BDc1caF0' //Add your wallet address here.
 
  const nonce = await web3.eth.getTransactionCount(myAddress, 'latest'); // nonce starts counting from 0

  const transaction = {
   'to': '0x78c115F1c8B7D0804FbDF3CF7995B030c512ee78', // faucet address to return eth
   'value': 200, // This is the amount we wish to send in wei
   'gas': 6000000, // to assess the right gas price you can check actual gas prices at ropsten.etherscan.io
   'maxPriorityFeePerGas': 1000000108, //This is the maximum you are willing to pay per gas to execute the tx
   'nonce': nonce,
   // optional data field to send message or execute smart contract
  };
 
  const signedTx = await web3.eth.accounts.signTransaction(transaction, PRIVATE_KEY);
  
  web3.eth.sendSignedTransaction(signedTx.rawTransaction, function(error, hash) {
  if (!error) {
    console.log("🎉 The hash of your transaction is: ", hash);
  } else {
    console.log("❗Something went wrong while submitting your transaction:", error)
  }
 });
}

main();

Run the code

node transaction.js

Example Successful Response

[Running] node "/send-tx/transaction.js"
🎉 The hash of your transaction is:  0x6a6e88b10a018487629409dbf3c3c08fced94e5ca381abf54279df593bb48b5a

[Done] exited with code=0 in 88.637 seconds

You can verify your balance in your wallet.

💡

Useful Resources

Get Started

🙌🏽 Super excellent job!!!