jklepatch / eattheblocks

Source code for Eat The Blocks, a screencast for Ethereum Dapp Developers

Home Page:https://eattheblocks.com

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Error: cannot estimate gas

jfernandez31 opened this issue · comments

Hi can some one please help with this?

Error: cannot estimate gas; transaction may fail or may require manual gas limit (error={"reason":"cannot estimate gas; transaction may fail or may require manual gas limit","code":"UNPREDICTABLE_GAS_LIMIT","error":{"code":-32000,"response":"{"jsonrpc":"2.0","id":8,"error":{"code":-32000,"message":"gas required exceeds allowance (0)"}}"},"method":"estimateGas","transaction

here is my config

const ethers = require('ethers');

const addresses = {
WBNB: '0xbb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c',
factory: '0xcA143Ce32Fe78f1f7019d7d551a6402fC5350c73',
router: '0x10ED43C718714eb63d5aA57B78B54704E256024E',
recipient: ''

//First address of this mnemonic must have enough BNB to pay for tx fess
const mnemonic = '';

const provider = new ethers.providers.WebSocketProvider('wss://');
const wallet = ethers.Wallet.fromMnemonic(mnemonic);
const account = wallet.connect(provider);
const factory = new ethers.Contract(
['event PairCreated(address indexed token0, address indexed token1, address pair, uint)'],
const router = new ethers.Contract(
'function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)',
'function swapExactTokensForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)'

const wbnb = new ethers.Contract(
'function approve(address spender, uint amount) public returns(bool)',

const init = async () => {
const tx = await wbnb.approve(
const receipt = await tx.wait();
console.log('Transaction receipt');

factory.on('PairCreated', async (token0, token1, pairAddress) => {
console.log(New pair detected ================= token0: ${token0} token1: ${token1} pairAddress: ${pairAddress});

//The quote currency needs to be WBNB (we will pay with WBNB)
let tokenIn, tokenOut;
if(token0 === addresses.WBNB) {
tokenIn = token0;
tokenOut = token1;

if(token1 == addresses.WBNB) {
tokenIn = token1;
tokenOut = token0;

//The quote currency is not WBNB
if(typeof tokenIn === 'undefined') {

//We buy for 0.1 BNB of the new token
//ethers was originally created for Ethereum, both also work for BSC
//'ether' === 'bnb' on BSC
const amountIn = ethers.utils.parseUnits('0.01', '9');
const amounts = await router.getAmountsOut(amountIn, [tokenIn, tokenOut]);
//Our execution price will be a bit different, we need some flexbility
const amountOutMin = amounts[1].sub(amounts[1].div(10));
console.log(Buying new token ================= tokenIn: ${amountIn.toString()} ${tokenIn} (WBNB) tokenOut: ${amountOutMin.toString()} ${tokenOut});
const tx = await router.swapExactTokensForTokens(
[tokenIn, tokenOut],
Date.now() + 1000 * 60 * 10 //10 minutes
const receipt = await tx.wait();
console.log('Transaction receipt');


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