How can my EVM smart contract send tokens to other blockchains via IBC?

Sei provides an IBC Precompile at address 0x0000000000000000000000000000000000001009 that enables EVM smart contracts to initiate IBC (Inter-Blockchain Communication) token transfers.

Key Functions (Solidity Interface):

interface ISeiIbcPrecompile {
    /**
     * @notice Initiates an IBC transfer with explicitly specified timeout parameters.
     * @dev Caller's EVM address must be associated. msg.value must be 0.
     * @param receiver The recipient address on the destination chain (string format).
     * @param sourcePort The source port on Sei (e.g., "transfer").
     * @param sourceChannel The source channel ID on Sei (e.g., "channel-0").
     * @param denom The denomination of the token to send (e.g., "usei", "ibc/HASH...").
     * @param amount The amount of the token to send (in its base unit).
     * @param revisionNumber The revision number part of the timeout height on the destination chain.
     * @param revisionHeight The revision height part of the timeout height on the destination chain.
     * @param timeoutTimestamp The absolute timestamp (in nanoseconds) after which the transfer times out.
     * @param memo An optional memo string for the IBC transfer.
     * @return success True if the IBC transfer message was successfully submitted.
     */
    function transfer(
        string memory receiver,
        string memory sourcePort,
        string memory sourceChannel,
        string memory denom,
        uint256 amount,
        uint64 revisionNumber,
        uint64 revisionHeight,
        uint64 timeoutTimestamp,
        string memory memo
    ) external returns (bool success);

    /**
     * @notice Initiates an IBC transfer using automatically calculated default timeout parameters.
     * @dev Caller's EVM address must be associated. msg.value must be 0.
     * @param receiver The recipient address on the destination chain (string format).
     * @param sourcePort The source port on Sei (e.g., "transfer").
     * @param sourceChannel The source channel ID on Sei (e.g., "channel-0").
     * @param denom The denomination of the token to send (e.g., "usei", "ibc/HASH...").
     * @param amount The amount of the token to send (in its base unit).
     * @param memo An optional memo string for the IBC transfer.
     * @return success True if the IBC transfer message was successfully submitted.
     */
    function transferWithDefaultTimeout(
        string memory receiver,
        string memory sourcePort,
        string memory sourceChannel,
        string memory denom,
        uint256 amount,
        string memory memo
    ) external returns (bool success);
}

How to Use:

1. Association: The EVM address (msg.sender) calling the precompile must be associated with a Sei native address. The native address is the actual sender of the IBC transfer.
2. Interface: Define or import the ISeiIbcPrecompile interface.
3. Instantiate: Get a reference: ISeiIbcPrecompile constant seiIbc = ISeiIbcPrecompile(0x0000000000000000000000000000000000001009);
4. Call Functions:
   • Choose transfer if you need precise control over the timeout height and timestamp.
   • Choose transferWithDefaultTimeout for convenience, allowing Sei to calculate reasonable defaults based on the current block and client state.
5. Parameters: Provide the recipient address on the destination chain, the correct sourcePort and sourceChannel for the desired route, the denom of the token being sent (this can be native usei or an IBC voucher denomination like ibc/HASH...), the amount (in the token's smallest unit), and an optional memo.

Important Considerations:

• Non-Payable: These functions are non-payable (msg.value must be 0). The tokens being transferred are deducted from the associated Sei native address's balance.
• No Delegate Call: This precompile cannot be called using delegatecall.
• Denominations: You can send native Sei tokens (like usei) or tokens that have arrived on Sei via IBC (represented by their ibc/... denom).
• Timeout: IBC transfers rely on timeouts. transferWithDefaultTimeout is generally recommended unless you have specific requirements for timeout calculation.
• IBC Knowledge: Using this precompile requires understanding IBC concepts like ports, channels, and destination chain address formats.
• Gas: While the precompile call itself has a base gas cost, the execution of the underlying IBC transfer involves interactions with multiple modules and relaying, which consumes Cosmos-level gas paid by the associated Sei native address.