Cross-Chain Two-Way Handshake System

This project implements a two-way handshake mechanism between smart contracts deployed on different blockchain networks (Base Sepolia and Sepolia) using a Go-based relayer service.

Overview

The system implements a three-step handshake process between two smart contracts:

1. SYN: Contract A initiates the handshake by sending a SYN message to Contract B
2. ACK: Contract B responds to the SYN message by sending an ACK back to Contract A
3. SYN-ACK: Contract A confirms receipt of the ACK by sending a SYN-ACK to Contract B

The handshake is facilitated by a relayer service that listens for events on both chains and relays messages between the contracts.

Architecture

Smart Contracts

• Contract A: Deployed on Base Goerli (Chain ID: 84532)
• Contract B: Deployed on Sepolia (Chain ID: 11155111)

Relayer Service

• Written in Go
• Listens for events on both chains simultaneously
• Handles transaction signing and submission
• Implements retry logic for failed transactions
• Prevents duplicate event processing

Prerequisites

• Go 1.16 or higher
• Contract A is in Base Sepolia and Contract B is in Sepolia
• Test ETH on both networks for gas fees
• A private key for the relayer account

Configuration

1. Create a .env file in the project root with the following variables:

# Network RPC URLs
NETWORK_A_RPC=https://sepolia.base.org
NETWORK_B_RPC=https://rpc.sepolia.ethpandaops.io

# Contract Addresses
CONTRACT_A=0x...  # Base Sepolia contract address
CONTRACT_B=0x...  # Sepolia contract address

# Contract ABIs
CONTRACT_A_ABI=[...]  # JSON array of Contract A ABI
CONTRACT_B_ABI=[...]  # JSON array of Contract B ABI

# Relayer Configuration
RELAYER_PRIVATE_KEY=0x...  # Private key for the relayer account

Installation

1. Clone the repository:

git clone <repository-url>
cd relayer_project

2. Install dependencies:

go mod download

3. Configure your environment:

cp .env.example .env
# Edit .env with your values

Usage

1. Start the relayer:

go run relayer.go

The relayer will:

• Connect to both networks
• Start listening for events
• Print the current block numbers on both chains
• Begin processing events and relaying messages

Error Handling

The system includes several error handling mechanisms:

• Retry logic for failed transactions
• Nonce management for transaction ordering
• Duplicate event detection
• Network connection error handling
• Gas estimation fallbacks

Monitoring

The relayer provides detailed logging:

• Transaction submission details
• Event detection
• Error messages
• Network status updates