Vara ↔ Ethereum Cross-Chain Ping

This is a minimal working example of a cross-chain application (Ping) demonstrating secure message delivery from the Vara network to Ethereum via the Vara ↔ Ethereum Bridge.

The project consists of three main components:

• cross-ping/ – The Vara-side program (Rust): sends a cross-chain Ping message.
• relayer/ – The permissionless relayer (Node.js): delivers messages and proofs from Vara to Ethereum.
• ping-receiver/ – The destination contract (Solidity): receives messages and emits a Pong event on Ethereum.

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Run Order

To run the Vara ↔ Ethereum Cross-Chain Ping example end-to-end, follow these steps:

1. Deploy the Solidity Receiver Contract (ping-receiver)

   • Deploy PingReceiver.sol to Ethereum (Holesky testnet).
   • Save the deployed contract address for use in the next step.

2. Deploy the Vara Contract (cross-ping)

   • Deploy the cross-ping program to the Vara network (testnet).
   • When deploying, set the destination parameter to the Ethereum address of your deployed PingReceiver contract.

3. Configure and Start the Relayer

   • In the relayer/ directory, create a .env file with all required RPC endpoints and contract addresses.
   • Install dependencies and start the relayer:

4. Send a Ping Message from Vara

   • Call the ping function in your Vara contract to initiate a cross-chain message.
   • The relayer will automatically detect, process, and deliver the message to Ethereum.

5. Check Delivery

   • In the relayer console, verify message processing and transaction hash.
   • On Ethereum (e.g., Etherscan), confirm that your PingReceiver contract emitted the PongEmitted event.

Note:
Merkle Root updates on the Ethereum side will take some time (typically around 10–20 minutes), so message delivery will not be instant.

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What does this example show?

• End-to-end flow: How to send, relay, and receive a message across two independent blockchains using trustless infrastructure.
• Minimal, production-like code: All business logic is in the application layer, while cryptographic security and cross-chain proof-of-delivery are handled by the bridge protocol.

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This example is intended for developers interested in cross-chain messaging, bridge integration, and hands-on experimentation. It can serve as a reference for more advanced cross-chain applications (tokens, DeFi, NFT, etc.).

Learn more about the Vara ↔ Ethereum Bridge:
wiki.vara.network/docs/bridge