How to Listen to Deposits on the opBNB Bridge

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TLDR:

Introduction to opBNB

opBNB is an EVM-compatible Layer 2 network built on the Optimism OP Stack, designed to scale the BNB Smart Chain. Key features:

By listening to deposit events, developers can track asset movements and integrate real-time data into applications.

Prerequisites

  1. Chainstack account (Sign up here) to deploy an opBNB node.
  2. Node.js (v18+ recommended).
  3. ethers.js library (npm install ethers).

Step-by-Step Guide

Step 1: Deploy an opBNB Node

Step 2: Initialize Project

mkdir opbnb-listener && cd opbnb-listener  
npm init -y  
npm install ethers

Step 3: Create Event Listener Script

Create index.js and paste the following:

const { ethers } = require("ethers");  

// Configure provider  
const provider = new ethers.JsonRpcProvider("YOUR_CHAINSTACK_NODE");  

// opBNB Bridge contract address  
const bridgeAddress = "0x4200000000000000000000000000000000000010";  

// ABI for DepositFinalized event  
const abi = ["event DepositFinalized(address indexed from, address indexed to, uint256 amount, bytes data)"];  

// Create contract instance  
const contract = new ethers.Contract(bridgeAddress, abi, provider);  

// Listen for events  
contract.on("DepositFinalized", (from, to, amount, data) => {  
  console.log(`New Deposit:  
    Sender: ${from}  
    Receiver: ${to}  
    Amount: ${ethers.formatEther(amount)} BNB  
    Data: ${data}  
  `);  
});  

console.log("Listening for deposits...");

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Code Breakdown

  1. Provider Setup: Connects to your opBNB node via JSON-RPC.
  2. Contract ABI: Defines the DepositFinalized event structure.
  3. Event Listener: Logs deposit details (sender, receiver, amount) in real-time.

FAQ

1. What is the opBNB Bridge contract address?

The official proxy address is 0x4200000000000000000000000000000000000010.

2. Can I filter deposits by specific tokens?

Yes! Modify the ABI to include token address parameters.

3. How do I handle historical events?

Use contract.queryFilter() to fetch past deposits.

👉 Explore advanced ethers.js techniques

Conclusion

This tutorial equipped you to track deposits on the opBNB Bridge using ethers.js. Key takeaways:

Next steps: