jw122 / layerzero

Experiments with LayerZero, the protocol for cross-chain messaging

LayerZero

Experiments with LayerZero, the protocol for cross-chain messaging

MultiChainCounter

Source: https://github.com/LayerZero-Labs/solidity-examples

This is a classic example of a simple contract implementing a counter, but on another chain.

The MultiChainCounter contract can send and receive LayerZero messages. This contract has to be deployed on both the source chain and the destination chain. I attempted this with testnets on Ethereum (Rinkeby) and Polygon (Mumbai).

Making use of LayerZero involves implementing a way to call send() and lzReceive()

Every contract is a ILayerZeroReceiver

Sending a message from Chain A

To send a message a message, we call the endpoint.send() function from the source chain:

endpoint.send{value:msg.value}(10001, destUaAddr, bytes("hello"), msg.sender, address(this), bytes(""));

send() has a few parameters: destination chainId, destination contract address, raw bytes of payload, where additional destination gas is refunded, address, tx parameters)

Receiving a message from Chain B

Your User Application contract must override the lzReceive() function. Any logic can be executed on the receiving chain.

The destination chain will execute lzReceive to receive the message.

Testing

I deployed contracts using REMIX. Had to include the interfaces as well, which get imported in MultiCoinCounter.sol

You must deploy the contract with an Endpoint address. An endpoint is the main LayerZero contract you interact with. An instance of Endpoint.sol is used to send messages to another chain via the endpoint.send() function.

See addresses for testnet

Contracts deployed:

Polygon (Mumbai): https://mumbai.polygonscan.com/address/0x57d2cf90ddce622fd98677db36d1a7051d991070

Ethereum (rinkeby): https://rinkeby.etherscan.io/address/0x9e799d14d9b042f1e9a85e66e7eb38affe16045b

You can load in these contracts from REMIX, and trigger the functions manually using injected Web3 (MetaMask).