Your First Cross-Chain Message
In this tutorial we will create a simple contract that allows sending a message from one chain to another using the Connector API.
Set up your environment
git clone https://github.com/zeta-chain/template
Install the dependencies:
yarn add --dev @openzeppelin/contracts
Create a new contract
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The sendHelloWorld function is used to send a "Hello, Cross-Chain World!"
message to another chain. It first checks the validity of the destination chain
ID. Then it fetches the required ZETA from the native chain token provided in
the transaction value, and approves the connector for the calculated Zeta value.
Then, it sends the message using the connector's send function.
The onZetaMessage function is used to handle incoming cross-chain messages. It
verifies the message signature and the message type. If it's a valid "Hello,
Cross-Chain World!" message, it emits a HelloWorldEvent with the message data.
The onZetaRevert function is triggered if a message fails to send. It decodes
the message similarly to onZetaMessage and emits a RevertedHelloWorldEvent
in case of failure.
Create a deployment task
To establish cross-chain messaging between blockchains via ZetaChain, you should deploy identical contracts on two or more connected chains.
You can specify the desired chains by adding a --networks parameter to the
deploy task, which accepts a list of network names separated by commas. For
instance, --networks goerli,bsc-testnet.
The main function maintains a mapping of network names to their corresponding deployed contract addresses, iterating over the networks to deploy the contract on each one.
The contract's constructor requires three arguments: the connector contract's
address, the ZETA token's address, and the ZETA token consumer contract's
address. These addresses are obtained using ZetaChain's getAddress.
The main function subsequently sets interactors for each contract. An interactor is a mapping between a chain ID of the destination and the contract address on that chain.
When deploying to two chains (like Goerli and BSC testnet), you will invoke
setInteractorByChainId on a Goerli contract and pass the BSC testnet chain ID
(97) and the BSC testnet contract address. You then perform the same operation
on a BSC testnet contract, passing the Goerli chain ID (5) and the Goerli
contract address. If deploying to more than two chains, you must call
setInteractorByChainId for each link between the chains.
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Clear the cache and artifacts, then compile the contract:
npx hardhat compile --force
Run the following command to deploy the contract to two networks:
npx hardhat deploy --networks bsc-testnet,goerli
🚀 Successfully deployed contract on bsc-testnet.
📜 Contract address: 0x6Fd784c16219026Ab0349A1a8A6e99B6eE579C93
🚀 Successfully deployed contract on goerli.
📜 Contract address: 0xf1907bb130feb28D6e1305C53A4bfdb32140d8E6
🔗 Setting interactors for a contract on bsc-testnet
✅ Interactor address for 5 (goerli) is set to 0xf1907bb130feb28d6e1305c53a4bfdb32140d8e6
🔗 Setting interactors for a contract on goerli
✅ Interactor address for 97 (bsc-testnet) is set to 0x6fd784c16219026ab0349a1a8a6e99b6ee579c93
Send a message
Create a new task to send a message from one chain to another. The task accepts two parameters: the contract address and the destination chain ID.
The task calls sendHelloWorld on the contract, passing the arguments.
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Send a message from BSC testnet to Goerli (chain ID: 5) using the contract
address (see the output of the deploy task). Make sure to submit enough native
tokens with --amount to pay for the transaction fees.
npx hardhat message --network bsc-testnet --destination 5 --contract 0x6Fd784c16219026Ab0349A1a8A6e99B6eE579C93 --amount 2
🔑 Using account: 0x2cD3D070aE1BD365909dD859d29F387AA96911e1
✅ "sendHelloWorld" transaction has been broadcasted to bsc-testnet
📝 Transaction hash: 0xa3a507d34056f4c00b753e7d0b47b16eb6d35b3c5016efa0323beb274725b1a1
Please, refer to ZetaChain's explorer for updates on the progress of
the cross-chain transaction.
🌍 Explorer: https://explorer.zetachain.com/cc/tx/0xa3a507d34056f4c00b753e7d0b47b16eb6d35b3c5016efa0323beb274725b1a1
After the cross-chain transaction is processed on ZetaChain, look up the
contract on the Goerli explorer by the contract address
(0xf1907bb130feb28D6e1305C53A4bfdb32140d8E6) and you should be able to see the
emitted HelloWorldEvent event.
Source Code
You can find the source code for the example in this tutorial here:
https://github.com/zeta-chain/example-contracts/blob/feat/import-toolkit/messaging/message