Quickstart - Create Your First Omnichain App

npx create-lz-oapp@latest

// contracts/MyOApp.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.22;

import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
import { OApp, MessagingFee, Origin } from "@layerzerolabs/oapp-evm/contracts/oapp/OApp.sol";
import { MessagingReceipt } from "@layerzerolabs/oapp-evm/contracts/oapp/OAppSender.sol";

contract MyOApp is OApp {
    constructor(address _endpoint, address _delegate) OApp(_endpoint, _delegate) Ownable(_delegate) {}

    // highlight-next-line
    // This is where the message will be stored after it is received on the destination chain
    // highlight-next-line
    string public data = "Nothing received yet.";

    /**
     * @notice Sends a message from the source chain to a destination chain.
     * @param _dstEid The endpoint ID of the destination chain.
     * @param _message The message string to be sent.
     * @param _options Additional options for message execution.
     * @dev Encodes the message as bytes and sends it using the `_lzSend` internal function.
     * @return receipt A `MessagingReceipt` struct containing details of the message sent.
     */
    function send(
        uint32 _dstEid,
        // highlight-next-line
        // The message to be sent to the destination chain
        // highlight-next-line
        string memory _message,
        bytes calldata _options
    ) external payable returns (MessagingReceipt memory receipt) {
        bytes memory _payload = abi.encode(_message);
        receipt = _lzSend(_dstEid, _payload, _options, MessagingFee(msg.value, 0), payable(msg.sender));
    }

    /**
     * @notice Quotes the gas needed to pay for the full omnichain transaction in native gas or ZRO token.
     * @param _dstEid Destination chain's endpoint ID.
     * @param _message The message.
     * @param _options Message execution options (e.g., for sending gas to destination).
     * @param _payInLzToken Whether to return fee in ZRO token.
     * @return fee A `MessagingFee` struct containing the calculated gas fee in either the native token or ZRO token.
     */
    function quote(
        uint32 _dstEid,
        string memory _message,
        bytes memory _options,
        bool _payInLzToken
    ) public view returns (MessagingFee memory fee) {
        bytes memory payload = abi.encode(_message);
        fee = _quote(_dstEid, payload, _options, _payInLzToken);
    }

    /**
     * @dev Internal function override to handle incoming messages from another chain.
     * @dev _origin A struct containing information about the message sender.
     * @dev _guid A unique global packet identifier for the message.
     * @param payload The encoded message payload being received.
     *
     * @dev The following params are unused in the current implementation of the OApp.
     * @dev _executor The address of the Executor responsible for processing the message.
     * @dev _extraData Arbitrary data appended by the Executor to the message.
     *
     * Decodes the received payload and processes it as per the business logic defined in the function.
     */
    function _lzReceive(
        Origin calldata /*_origin*/,
        bytes32 /*_guid*/,
        bytes calldata payload,
        address /*_executor*/,
        bytes calldata /*_extraData*/
    ) internal override {
        data = abi.decode(payload, (string));
    }
}

networks: {
    'avalanche-testnet': {
        eid: EndpointId.AVALANCHE_V2_TESTNET,
        url: process.env.RPC_URL_FUJI || 'https://rpc.ankr.com/avalanche_fuji',
        accounts,
    },
    'amoy-testnet': {
        eid: EndpointId.AMOY_V2_TESTNET,
        url: process.env.RPC_URL_AMOY || 'https://polygon-amoy-bor-rpc.publicnode.com',
        accounts,
    },
}

PRIVATE_KEY = your_private_key; // Required
RPC_URL_FUJI = your_fuji_rpc; // Optional but recommended
RPC_URL_AMOY = your_amoy_rpc; // Optional but recommended

npx hardhat lz:deploy

// layerzero.config.ts
import {EndpointId} from '@layerzerolabs/lz-definitions';

import type {OAppOmniGraphHardhat, OmniPointHardhat} from '@layerzerolabs/toolbox-hardhat';

const fujiContract: OmniPointHardhat = {
  eid: EndpointId.AVALANCHE_V2_TESTNET,
  contractName: 'MyOApp',
};

const amoyContract: OmniPointHardhat = {
  eid: EndpointId.AMOY_V2_TESTNET,
  contractName: 'MyOApp',
};

const config: OAppOmniGraphHardhat = {
  contracts: [
    {
      contract: fujiContract,
    },
    {
      contract: amoyContract,
    },
  ],
  // highlight-start
  connections: [
    {
      from: fujiContract,
      to: amoyContract,
    },
    {
      from: amoyContract,
      to: fujiContract,
    },
  ],
  // highlight-end
};

export default config;

npx hardhat lz:oapp:wire --oapp-config layerzero.config.ts

npx hardhat lz:oapp:peers:get --oapp-config layerzero.config.ts

// tasks/sendMessage.ts

import {task} from 'hardhat/config';
import {HardhatRuntimeEnvironment} from 'hardhat/types';

import {Options} from '@layerzerolabs/lz-v2-utilities';

export default task('sendMessage', 'Send a message to the destination chain')
  .addParam('dstNetwork', 'The destination network name (from hardhat.config.ts)')
  .addParam('message', 'The message to send')
  .setAction(async (taskArgs, hre: HardhatRuntimeEnvironment) => {
    const {message, dstNetwork} = taskArgs;
    const [signer] = await hre.ethers.getSigners();

    // Get destination network's EID
    const dstNetworkConfig = hre.config.networks[dstNetwork];
    const dstEid = dstNetworkConfig.eid;

    // Get current network's EID
    const srcNetworkConfig = hre.config.networks[hre.network.name];
    const srcEid = srcNetworkConfig?.eid;

    console.log('Sending message:');
    console.log('- From:', signer.address);
    console.log('- Source network:', hre.network.name, srcEid ? `(EID: ${srcEid})` : '');
    console.log('- Destination:', dstNetwork || 'unknown network', `(EID: ${dstEid})`);
    console.log('- Message:', message);

    const myOApp = await hre.deployments.get('MyOApp');
    const contract = await hre.ethers.getContractAt('MyOApp', myOApp.address, signer);

    // Add executor options with gas limit
    const options = Options.newOptions().addExecutorLzReceiveOption(200000, 0).toBytes();

    // Get quote for the message
    console.log('Getting quote...');
    const quotedFee = await contract.quote(dstEid, message, options, false);
    console.log('Quoted fee:', hre.ethers.utils.formatEther(quotedFee.nativeFee));

    // Send the message
    console.log('Sending message...');
    const tx = await contract.send(dstEid, message, options, {value: quotedFee.nativeFee});

    const receipt = await tx.wait();
    console.log('🎉 Message sent! Transaction hash:', receipt.transactionHash);
    console.log(
      'Check message status on LayerZero Scan: https://testnet.layerzeroscan.com/tx/' +
        receipt.transactionHash,
    );
  });

// hardhat.config.ts
// (...)
import {EndpointId} from '@layerzerolabs/lz-definitions';
import './tasks/sendMessage'; // Import the task

npx hardhat sendMessage --network avalanche-testnet --dst-network amoy-testnet --message "Hello Omnichain World (sent from Avalanche)"

// contracts/MyOApp.sol
// (...)
string public data = "Nothing received yet.";