# Chain-Data Query

### <mark style="color:blue;">Connecting to Filecoin networks via public RPC nodes</mark>

To query chain state and data on any Filecoin network, it is necessary to connect to public node providers. However, it's important to note that most public node providers offer limited access, typically allowing read-only JSON RPC calls and `MPoolPush` to send signed messages to the Filecoin networks.

To explore further details about the available public RPC providers supporting Filecoin mainnet and Calibration testnet, you can refer to the following page.

* [Filecoin mainnet RPCs](https://docs.filecoin.io/networks/mainnet/rpcs)
* [Filecoin Calibration testnet RPCs](https://docs.filecoin.io/networks/calibration/rpcs)

#### **Ingredients**

Let's use Glif nodes as an example to demonstrate how to connect to a public Filecoin RPC node provider. Additionally, we will utilize `ethers.js` to establish the connection with the RPC nodes.

* [Glif nodes](https://hosting.glif.io/)
* [ethers.js](https://docs.ethers.org/v5/)

#### **Instructions**

We will use `ethers.js` to establish a connection with the public Filecoin node provided by Glif. The following code demonstrates connecting to the Filecoin Calibration testnet as an example.

```javascript
import { ethers } from "ethers"

//The public Filecoin calibration URL
const filecoin_url = 'https://api.calibration.node.glif.io/rpc/v1'
const provider = new ethers.JsonRpcProvider(filecoin_url)

const blockNumber = await provider.getBlockNumber()
console.log("Block height: ", blockNumber)

```

The expected output:

```
Block height:  1268350
```

***

### <mark style="color:blue;">Listen to smart contract events</mark>

Since the Filecoin Virtual Machine (FVM) is EVM-compatible, we can use `ethers.js` to listen to smart contract events for specific contract actions on the Filecoin network. For instance, we can monitor ERC20 token `transfer` events or client contract `DealProposalCreate` events.

#### **Ingredients**

We will also use `ethers.js` to connect to the public Glif node to listen to the smart contract events.

* [Glif Nodes](https://hosting.glif.io/)
* [ethers.js](https://docs.ethers.org/v5/)

#### **Instructions**

Let's consider the [wFIL contract](https://docs.filecoin.io/smart-contracts/advanced/wrapped-fil), an ERC-20 token on Filecoin, as an example for listening to its transfer event. To demonstrate how to listen to smart contract events using ethers, we will use the deployed wFIL token address on the Filecoin calibration network and a simplified ABI object for the transfer event. Typically, you would have the wFIL smart contract's Application Binary Interface (ABI) defined in an `abi.json` file.

The code to listen to `transfer` events for the wFIL token.

```javascript
import { ethers } from "ethers"

const wFILAddress = "0xaC26a4Ab9cF2A8c5DBaB6fb4351ec0F4b07356c4" // wFIL Contract
var abi = ["event Transfer(address indexed from, address indexed to, uint amount)"]

const filecoin_url = 'https://api.calibration.node.glif.io/rpc/v1'
const provider = new ethers.providers.JsonRpcProvider(filecoin_url)

//listen to the Transfer events in the Token contract
const wFIL = new ethers.Contract(wFILAddress, abi, provider)
wFIL.on("Transfer", (from, to, value, event)=>{
    let transferEvent ={
        from: from,
        to: to,
        value: value,
        eventData: event,
    }
    console.log(JSON.stringify(transferEvent, null, 4))
})
```

Once a wFIL token transfer is executed on the blockchain, the following code snippet will capture the corresponding events and print out the event details.

***

### <mark style="color:blue;">Filter smart contract events</mark>

We can also use filters to retrieve specific smart contract transactions from the Filecoin network. Filters enable us to define criteria or conditions to search for event logs that match specific requirements. By setting up a filter, we can monitor and retrieve event logs related to our interests or specific smart contracts.

#### **Ingredients**

We will also use `ethers.js` to connect to the public Glif node to filter the smart contract events by providing conditions.

* [Glif nodes](https://hosting.glif.io/)
* [ethers.js](https://docs.ethers.org/v5/)

#### **Instructions**

Here's an example of how you can connect to a Glif node on the calibration network, create a filter to list all wFIL token transfers from your address, and execute the filter to look back 2000 blocks to find the matched transaction list:

```javascript
import { ethers } from "ethers"

const wFILAddress = "0xaC26a4Ab9cF2A8c5DBaB6fb4351ec0F4b07356c4" // wFIL Contract
var abi = ["event Transfer(address indexed from, address indexed to, uint amount)"]

const filecoin_url = 'https://api.calibration.node.glif.io/rpc/v1'
const provider = new ethers.providers.JsonRpcProvider(filecoin_url)

// Create a filter to list all token transfers from myAddress
const filter = contract.filters.Transfer("0xd388aB098ed3E84c0D808776440B48F685198498");

//Filter on the events back to 2000 blocks. 
const currentBlockHight = await provider.getBlockNumber();
const result = await contract.queryFilter(filter,currentBlockHight-2000, currentBlockHight );
console.log(result);
```

The expected transaction will be similar as follows. With this information, you can develop custom logic to efficiently track and process specific events or blocks on your FEVM smart contracts.

```json
{
    blockNumber: 1268728,
    blockHash: '0x7b4f34d3f7ef791da7f9ab1c342cf147eedf7ec4f99fe92b94a9372927779961',
    transactionIndex: 0,
    removed: false,
    address: '0xb44cc5FB8CfEdE63ce1758CE0CDe0958A7702a16',
    data: '0x0000000000000000000000000000000000000000000000001bc16d674ec80000',
    topics: [
      '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
      '0x000000000000000000000000d388ab098ed3e84c0d808776440b48f685198498',
      '0x00000000000000000000000044061aa8df5b33a997ce97d80c700d0c655dc3f2'
    ],
    transactionHash: '0x7adb72ac19bf6baa5176f5da799128140ea3a9a9306bf6b1ff52edc58c621c4b',
    logIndex: 0,
    removeListener: [Function (anonymous)],
    getBlock: [Function (anonymous)],
    getTransaction: [Function (anonymous)],
    getTransactionReceipt: [Function (anonymous)],
    event: 'Transfer',
    eventSignature: 'Transfer(address,address,uint256)',
    decode: [Function (anonymous)],
    args: [
      '0xd388aB098ed3E84c0D808776440B48F685198498',
      '0x44061AA8Df5b33a997CE97d80c700d0C655Dc3f2',
      [BigNumber],
      from: '0xd388aB098ed3E84c0D808776440B48F685198498',
      to: '0x44061AA8Df5b33a997CE97d80c700d0C655Dc3f2',
      amount: [BigNumber]
    ]
  },
```

[Was this page helpful?](https://airtable.com/apppq4inOe4gmSSlk/pagoZHC2i1iqgphgl/form?prefill_Page+URL=https://docs.filecoin.io/builder-cookbook/dapps/chain-data-query)


---

# 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://docs.filecoin.io/builder-cookbook/dapps/chain-data-query.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.