eth_subscribe - Polygon

Example code for the eth_subscribe json-rpc method. Сomplete guide on how to use eth_subscribe json-rpc in GetBlock.io Web3 documentation.

The eth_subscribe method creates a subscription over WebSocket to receive real-time notifications for new blocks, pending transactions, or logs matching specified criteria.

This method requires a WebSocket connection.

Parameters

Parameter	Type	Required	Description
subscriptionType	string	Yes	Subscription type: "newHeads", "newPendingTransactions", "logs"
filterObject	object	No	Filter options for log subscriptions

Request

cURL

cURL (wscat)

# This method requires WebSocket connection
wscat -c wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/

> {"jsonrpc":"2.0","method":"eth_subscribe","params":["newheads"],"id":"getblock.io"}

Javascript

JavaScript (ws)

const WebSocket = require('ws');

const ws = new WebSocket('wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/');

ws.on('open', () => {
    ws.send(JSON.stringify({
        jsonrpc: '2.0',
        method: 'eth_subscribe',
        params: ['newHeads'],
        id: 'getblock.io'
    }));
});

ws.on('message', (data) => {
    console.log(JSON.parse(data));
});

Python

Python (websockets)

import asyncio
import websockets
import json

async def unsubscribe():
    uri = "wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/"
    async with websockets.connect(uri) as ws:
        payload = {
            "jsonrpc": "2.0",
            "method": "eth_subscribe",
            "params": ["newHeads"],
            "id": "getblock.io"
        }
        await ws.send(json.dumps(payload))
        response = await ws.recv()
        print(json.loads(response))

asyncio.run(unsubscribe())

Rust

Rust (tokio-tungstenite)

use tokio_tungstenite::connect_async;
use futures_util::{SinkExt, StreamExt};
use serde_json::json;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let url = "wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/";
    let (mut ws, _) = connect_async(url).await?;
    
    let payload = json!({
        "jsonrpc": "2.0",
        "method": "eth_subscribe",
        "params": ["newHeads"],
        "id": "getblock.io"
    });
    
    ws.send(payload.to_string().into()).await?;
    
    if let Some(msg) = ws.next().await {
        println!("{:?}", msg?);
    }
    
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x9cef478923ff08bf67fde6c64013158d"
}

Response Parameters

Field	Type	Description
jsonrpc	string	JSON-RPC version (2.0)
id	string	Request identifier
result	varies	Subscription ID for receiving notifications

Use Case

The eth_subscribe method is useful for:

• Real-time block monitoring

• Event streaming

• Live transaction tracking

Error Handling

Status Code	Error Message	Cause
403	Forbidden	Missing or invalid ACCESS-TOKEN
-32600	Invalid Request	Malformed request body
-32602	Invalid params	Invalid method parameters

Web3 Integration

Ethers.js

ethers.js example

import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/');

const result = await provider.send('eth_subscribe', ["newHeads"]);
console.log('Result:', result);

Viem

viem example

import { createPublicClient, http } from 'viem';
import { polygon } from 'viem/chains';

const client = createPublicClient({
    chain: polygon,
    transport: http('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/')
});

const result = await client.request({
    method: 'eth_subscribe',
    params: ["newHeads"]
});
console.log('Result:', result);