# Send

Execute this function via an interface from a User-defined contract In this case, it is necessary to send the fee to be paid to [Relayer](/docs/protocol/relayer.md) as `msg.value`.

```solidity
struct QueryRequest {
  uint32 dstChainId;
  address to;
  uint256 height;
  bytes32 slot;
}

function query(
  QueryRequest[] memory queries,
  address lightClient,
  address callBack,
  bytes calldata message
) external;
```

<table><thead><tr><th width="174.5">Field</th><th>Description</th></tr></thead><tbody><tr><td><code>queries</code></td><td>An array of <code>QueryRequest</code> data</td></tr><tr><td><code>lightClient</code></td><td>The address of the contract is to be verified</td></tr><tr><td><code>callBack</code></td><td>The address of the contract to return the data to</td></tr><tr><td><code>message</code></td><td>Data to be returned, in addition to the query</td></tr></tbody></table>

What the `query` function does:

* Encode the query data
* Calculate the query Id
* Execute the light client process as necessary
  * Currently, sending a request to Chainlink's Node Operator
* Emit a request event
* Pay fees to [Relayer](/docs/protocol/relayer.md)
  * Calculate the transaction fee off-chain and send the token based on it

#### Calculate the query Id

```solidity
bytes memory encodedPayload = abi.encode(
	callBack,
	queries,
	message,
	lightClient
);
bytes32 queryId = keccak256(abi.encode(encodedPayload, nonce));
```

Encode each field and the nonce again and hash it as `queryId`.

#### Emit a request event

Events are emitted with the following structure;

```solidity
event Packet(
	address indexed sender,
  	bytes32 indexed queryId,
	bytes packet,
	bytes message,
	address lightClient,
	address callBack
);
```

<table><thead><tr><th width="187">Field</th><th>Description</th></tr></thead><tbody><tr><td><code>sender</code></td><td>An user who executed the contract</td></tr><tr><td><code>queries</code></td><td>An array of <code>QueryRequest</code> data</td></tr><tr><td><code>packet</code></td><td><code>callBack</code>, <code>queries</code>, <code>message</code>, <code>lightClient</code> encoded</td></tr><tr><td><code>message</code></td><td>Data to be returned, in addition to the query</td></tr><tr><td><code>lightClient</code></td><td>The address of the contract is to be verified</td></tr><tr><td><code>callBack</code></td><td>The address of the contract to return the data to</td></tr></tbody></table>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://futaba.gitbook.io/docs/protocol/gateway/send.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.