# Blocks

## Connection

The connection is managed using WebSockets, which connect directly to a VeChain node.

A simple connection can be established with this snippet:

```js
import WebSocket from 'ws';
const ws = new WebSocket('wss://mainnet.vechain.org/subscriptions/block');
ws.onmessage = (message) => {
    console.log('New block', message.data);
}
```

This will receive a new block as soon as it is added to the blockchain, in the form of JSON-encoded strings.

## Options

To resume listening from a specific block position, the options can include a `blockID` to continue from where a previous listener may have disconnected.

For additional details on the options, refer to the documentation of [`BlockSubscriptionOptions`](https://vechain.github.io/vechain-sdk-js/interfaces/_vechain_sdk_network.BlockSubscriptionOptions.html).

## Block Details

The blocks are received as JSON-encoded strings. These strings must be parsed into usable objects, resulting in an object of type [`BlockDetail`](https://vechain.github.io/vechain-sdk-js/interfaces/_vechain_sdk_network.BlockDetail.html).

An example result is:

```json
{
  number: 18342166,
  id: '0x0117e116630b0db7c0208cf0e01d9dfefcc400310e75e738ebafaeca221ae31d',
  size: 684,
  parentID: '0x0117e115cc9e7eab70f4513ab8d82517c2d6e5dee3c121f5caba9dbfe517587f',
  timestamp: 1713949450,
  gasLimit: 29999972,
  beneficiary: '0x0ffb1cbc86b3ad0a17292b7fda577d59c0d7aed9',
  gasUsed: 57454,
  totalScore: 1787902837,
  txsRoot: '0x00a3024aac1092060e5f9368dd364f9eb9918eddc2d5ecfd92c64faf506c5176',
  txsFeatures: 1,
  stateRoot: '0x3ffc3fecb7d43d982b712f38ea5c9324375bc0c8db9f54dae91bd07777905b9e',
  receiptsRoot: '0x186a987d166ec60daf5a54ef97344a47d5c6e5f816b51e8ae49b14a332aebbb1',
  com: true,
  signer: '0x9e1c86df9e17451c0177544aa9a55edb3e0581b0',
  transactions: [
    '0xecc1a99b0afcf25c3283babc91641ed57d7dd3e6ae9e78058c439ae8c476f543',
    '0x27af83997e4b045024eafdb6041a97097de8cd528a22176056d0652f81a98fc4'
  ],
  obsolete: false
}
```

## Example Project

{% embed url="<https://stackblitz.com/github/vechain-energy/example-snippets/tree/v1.0.0/sdk/listen-blocks?ctl=1&embed=1&file=index.mjs&hideExplorer=1&hideNavigation=1&view=editor>" %}


---

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

```
GET https://docs.vechain.org/developer-resources/how-to-build-on-vechain/listen-to-changes/blocks.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.