# Writing your message sending contract

Here’s how you write a contract on **Sepolia** that dispatches a message using Hashi’s **Yaho** contract. This message will be relayed to **Chiado** and trigger the callback.

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IYaho {
    function dispatchMessageToAdapters(
        uint256 targetChainId,
        uint256 threshold,
        address targetAddress,
        bytes memory data,
        address[] memory reporters,
        address[] memory adapters
    ) external;
}

contract SepoliaSender {
    IYaho public yaho = IYaho(0x21eAB033C7D2DF6A67AeF6C5Bda9A7F151eB9f52);  // Yaho address on Sepolia
    uint256 public threshold;
    address[] public reporters;
    address[] public adapters;

    constructor(address _yaho, uint256 _threshold, address[] memory _reporters, address[] memory _adapters) {
        threshold = _threshold;
        reporters = _reporters;
        adapters = _adapters;
    }

    // Function to send a cross-chain message to Chiado
    function sendMessageToChiado(
        uint256 targetChainId, 
        address targetAddress, 
        string memory _message
    ) public {
        bytes memory data = abi.encode(_message);
        yaho.dispatchMessageToAdapters(targetChainId, threshold, targetAddress, data, reporters, adapters);
    }
}
```

**Explanation**:

* The contract interacts with the **Yaho** contract on **Sepolia** to dispatch a message to **Chiado** using `dispatchMessageToAdapters`.
* The `sendMessageToChiado` function takes the target chain ID(10200 for Chiado), target address (ChiadoReceiver contract on Chiado), and the message to be sent.
* The **reporters**, **adapters**, and **threshold** are passed into the Yaho contract for cross-chain message validation and relaying.

**Deployment**:

* Deploy this contract on **Sepolia**, passing the **reporters**, **adapters**, and **threshold** into the constructor.
* A list of reporters and adapters contract can be found in: [Oracles](/hashi/core-concepts/oracles.md)
* Yaho contract address can be found in [Blockchains](/hashi/deployments/blockchains.md#yaho-and-yaru)
* `Threshold` must equal to `expectedThreshold` in Receiver contract.


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