A Developer's Guide to Sending Your First Cross-Chain Message with LayerZero

Traditional cross-chain communication involves slow, risky bridges. The LayerZero Omnichain Protocol introduces a new primitive for secure Cross-Chain Communication through its network of Endpoints. This guide gives a high-level overview of How to use LayerZero.

Core Concept: The Endpoint & Ultra Light Node
A look at the LayerZero Endpoint Explained shows it's a set of smart contracts that you deploy on each chain you want to communicate with. The magic happens with the LayerZero Ultra Light Node (ULN), which is far cheaper to run than a typical light node. It validates transaction proofs without keeping all block headers, making the process highly efficient.

The Security Architecture
The LayerZero Security Model is unique. It separates the roles of validating a transaction (the Oracle) and relaying a transaction (the Relayer). The system is only secure if these two independent entities do not collude. By default, LayerZero uses Chainlink as the Oracle, but developers can run their own.

Step 1: Setting up Your Endpoint
Deploy Endpoint Contract: Deploy the LayerZero Endpoint smart contract on each chain you want to support (e.g., Ethereum and Avalanche).

Configure Paths: In your dApp's smart contract, you'll configure the contract addresses of the other endpoints on different chains, creating a messaging path.

Step 2: Sending a Message
Sending a message is a simple function call.

Example: Sending a message from Ethereum to Avalanche (Solidity Pseudocode)

solidity
// Your contract on Ethereum
import "LayerZeroEndpoint.sol";

contract MyOmnichainApp {
LayerZeroEndpoint public endpoint;
uint16 destinationChainId; // Avalanche's LayerZero ID
address destinationAppAddress; // Your contract address on Avalanche

function sendMessage(string memory _message) public payable {
    // The core LayerZero function call
    endpoint.send{value: msg.value}(
        destinationChainId,
        destinationAppAddress,
        abi.encode(_message), // Your payload
        payable(msg.sender),
        address(0x0), // For adapter params
        "" // Library parameters
    );
}

}
This transaction is sent to the Oracle and Relayer. Once validated, the message is delivered to your contract on the destination chain. This is the foundation of building "omnichain" applications.

For full smart contract interfaces, please refer to https://sites.google.com/koinly-tax-reports.org/layerzero/.