Sending a Message

Concero allows you to send messages from one blockchain to another using the conceroSend function. This enables cross-chain communication for a variety of use cases such as cross-chain token transfers, governance actions, or any custom cross-chain interactions.

Function Signature

function conceroSend(
    uint24 dstChainSelector,
    bool shouldFinaliseSrc,
    address feeToken,
    ConceroTypes.EvmDstChainData memory dstChainData,
    bytes calldata message
) external payable returns (bytes32)

Parameters

Parameter	Type	Description
`dstChainSelector`	`uint24`	Identifier for the destination chain
`shouldFinaliseSrc`	`bool`	Flag for source chain finality (must be `false` as it's not yet supported)
`feeToken`	`address`	Token used to pay transaction fees (currently only native tokens are supported, so this must be `address(0)`)
`dstChainData`	`ConceroTypes.EvmDstChainData`	Structure containing destination chain execution parameters
`message`	`bytes`	The message payload to be sent to the destination chain

EvmDstChainData Structure

struct EvmDstChainData {
    address receiver;  // The contract to receive the message on the destination chain
    uint256 gasLimit;  // Gas limit for the message execution on the destination chain.
}

Return Value

Type	Description
`bytes32`	A unique message identifier that can be used to track the message

Usage Example

import {IConceroRouter} from "../interfaces/IConceroRouter.sol";
import {ConceroTypes} from "@concero/contracts/interfaces/ConceroTypes.sol";
import {ConceroClient} from "./ConceroClient.sol";
 
contract MessageSender {
  constructor(address conceroRouter) ConceroClient(conceroRouter) {}
 
  function sendCrossChainMessage(
      uint24 dstChainSelector,
      address receiver,
      uint256 gasLimit,
      bytes memory messageBody
  ) external payable {
 
      // 1. Quote message fee
      uint256 messageFeeNative = IConceroRouter(i_conceroRouter).getMessageFee(
        dstChainSelector,
        false, // Source chain finality not yet supported
        address(0), // Using native token for fees
        dstData
      );
 
      // 2. Prepare destination chain data
      ConceroTypes.EvmDstChainData memory dstData = ConceroTypes.EvmDstChainData({
        receiver: receiver,
        gasLimit: gasLimit
      });
 
      // 3. Send the cross-chain message
      bytes32 messageId = IConceroRouter(i_conceroRouter).conceroSend{value: messageFeeNative}(
        dstChainSelector,
        false, // Source chain finality not yet supported
        address(0), // Using native token for fees
        dstData,
        messageBody
      );
  }
}

Important Notes

Source chain finality is not yet supported, so shouldFinaliseSrc must be false
Currently only native value is supported for fee payment (ETH, MATIC, etc.)

ConceroMessageSent Event

When a message is sent, a ConceroMessageSent event is emitted with the following parameters:

event ConceroMessageSent(
    bytes32 indexed messageId,
    uint16 version,
    bool shouldFinaliseSrc,
    uint24 dstChainSelector,
    bytes dstChainData,
    address sender,
    bytes message
);