How to build Front running bot ?
A front-running bot (MEV bot that uses a sandwich attack strategy) consists of two main parts:
- Off-chain Bot: This part is responsible for detecting profitable transactions, constructing transactions, and broadcasting them to the MEV contract ( On-Chain Component ).
- On-chain Component (MEV Contract): This is a smart contract that executes the front-running and back-running transactions and manages the profits.
These components work together seamlessly to identify profitable transactions and execute them efficiently.
Off-Chain Component parts :
The off-chain component is responsible for Monitor pending transactions , detecting profitable transactions and constructing front-running and back-running transactions, and sending them to the On-Chain component .
1. Blockchain Node Connection (Simple Code)
First, we need to connect to a blockchain node. This connection allows us to monitor the mempool and submit transactions.
from web3 import Web3
# Connect to an Ethereum node
infura_url = "https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID"
web3 = Web3(Web3.HTTPProvider(infura_url))
if web3.isConnected():
print("Connected to Ethereum node")
else:
print("Failed to connect")
2. Mempool Scanner (Simple Code)
The mempool scanner continuously scans the mempool for pending transactions.
def get_pending_transactions():
block = web3.eth.getBlock('pending', full_transactions=True)
return block['transactions']
pending_txns = get_pending_transactions()
3. Transaction Analyzer (Simple Code)
The transaction analyzer examines the pending transactions to identify profitable opportunities.
def analyze_transaction(tx):
gas_price = tx['gasPrice']
to = tx['to']
input_data = tx['input']
return {
'gas_price': gas_price,
'to': to,
'input_data': input_data,
'is_profitable': check_profitability(gas_price, to, input_data)
}
def check_profitability(gas_price, to, input_data):
# Implement your own logic to check profitability
return True
analyzed_txns = [analyze_transaction(tx) for tx in pending_txns]
4. Transaction Constructor (Simple Code)
Once a profitable transaction is identified, we construct the data payloads for front-running and back-running transactions to send to the MEV contract.
def construct_data_payloads(tx):
contract = web3.eth.contract(address="MEV_CONTRACT_ADDRESS", abi=MEV_CONTRACT_ABI)
front_run_data = contract.functions.frontRun(tx['to'], tx['input_data']).buildTransaction()['data']
back_run_data = contract.functions.backRun(tx['to'], tx['input_data']).buildTransaction()['data']
return front_run_data, back_run_data
profitable_txns = [tx for tx in analyzed_txns if tx['is_profitable']]
data_payloads = [construct_data_payloads(tx) for tx in profitable_txns]
5. Interaction with MEV Contract (Simple Code)
The off-chain component sends the constructed data payloads to the MEV contract, which handles the transaction submissions.
def interact_with_mev_contract(front_run_data, back_run_data):
account = web3.eth.account.privateKeyToAccount("YOUR_PRIVATE_KEY")
nonce = web3.eth.getTransactionCount(account.address)
mev_tx = {
'nonce': nonce,
'gasPrice': web3.toWei(100, 'gwei'),
'gas': 1000000,
'to': "MEV_CONTRACT_ADDRESS",
'value': web3.toWei(0.01, 'ether'),
'data': front_run_data + back_run_data
}
signed_mev_tx = web3.eth.account.signTransaction(mev_tx, "YOUR_PRIVATE_KEY")
tx_hash = web3.eth.sendRawTransaction(signed_mev_tx.rawTransaction)
return tx_hash
for front_run_data, back_run_data in data_payloads:
tx_hash = interact_with_mev_contract(front_run_data, back_run_data)
print(f"MEV transaction sent with hash: {tx_hash.hex()}")
On-Chain Component ( MEV Solidity Contract ) :
The on-chain component consists of the MEV smart contract that executes the front-running and back-running trades and manages the profits.
1- MEV Smart Contract (Simple Code)
The smart contract receives the transaction data from the off-chain component and executes the sandwich attack strategy.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract MEVBot {
address public owner;
constructor() {
owner = msg.sender;
}
modifier onlyOwner() {
require(msg.sender == owner, "Not the contract owner");
_;
}
function frontRun(address target, bytes memory data) public payable onlyOwner {
(bool success, ) = target.call{value: msg.value}(data);
require(success, "Front-run execution failed");
}
function backRun(address target, bytes memory data) public payable onlyOwner {
(bool success, ) = target.call{value: msg.value}(data);
require(success, "Back-run execution failed");
}
function executeSandwichAttack(address target, bytes memory frontRunData, bytes memory backRunData) public payable onlyOwner {
frontRun(target, frontRunData);
backRun(target, backRunData);
}
function withdraw() public onlyOwner {
payable(owner).transfer(address(this).balance);
}
receive() external payable {}
}
Profit Analysis and Management (Simple Code)
After transactions are broadcasted, the off-chain component should monitor the blockchain to calculate profits and adjust strategies.
def calculate_profit(tx_hash):
receipt = web3.eth.waitForTransactionReceipt(tx_hash)
gas_used = receipt['gasUsed']
effective_gas_price = receipt['effectiveGasPrice']
transaction_cost = gas_used * effective_gas_price
profit = calculate_actual_profit(transaction_cost)
return profit
def calculate_actual_profit(transaction_cost):
# Implement your own logic to calculate actual profit
return 1 - transaction_cost
for front_run_data, back_run_data in data_payloads:
tx_hash = interact_with_mev_contract(front_run_data, back_run_data)
profit = calculate_profit(tx_hash)
print(f"Transaction profit: {profit} ETH")
Conclusion
This guide illustrates the interaction between off-chain and on-chain components in a sandwich attack bot. The off-chain component is responsible for detecting opportunities, constructing transactions, and interacting with the MEV contract. The on-chain component, consisting of the MEV smart contract, executes the front-running and back-running trades and manages profits. This comprehensive integration ensures the bot operates effectively within the blockchain ecosystem.
