Interact with a node RPC

If you're a new Web3 developer, it's unlikely that you'll need to run your own full node on Polygon.

The majority of developers use a node provider, or a third-party external service that receives node requests and returns responses for you automatically. That's because the fastest way to get developing on Polygon is using a node provider rather than managing your own node.

This guide demonstrates how to connect to a RPC provider, using Alchemy as an example.

Send your first blockchain request

This guide assumes you already have an Alchemy account and access to the Alchemy Dashboard.

Create an Alchemy key

First, you'll need an Alchemy API key to authenticate your requests. You can create API keys from the dashboard. Check out this YouTube video on how to create an app. Or you can follow the steps written below:

1. Navigate to the Create App button in the Apps tab.

2. Fill in the details under Create App to get your new key. You can also see the applications you previously made by you and your team on this page. Pull existing keys by clicking on View Key for any app.

Making a cURL request

You can interact with Alchemy's Polygon infrastructure provider using JSON-RPC and your command line interface.

For manual requests, use POST requests to interact with the JSON-RPC. Simply pass in the Content-Type: application/json header and your query as the POST body with the following fields:

• jsonrpc: The JSON-RPC version—currently, only 2.0 is supported.
• method: The MATIC API method. See API reference.
• params: A list of parameters to pass to the method.
• id: The ID of your request. Will be returned by the response so you can keep track of which request a response belongs to.

Example request

curl https://eth-mainnet.alchemyapi.io/jsonrpc/demo \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":73,"method":"eth_gasPrice","params":[]}'

Results:

{ "id": 73,
  "jsonrpc": "2.0",
  "result": "0x09184e72a000" // 10000000000000 }

Alchemy SDK setup

To make blockchain requests directly from your Javascript / Node.js dApp, you'll need to integrate the Alchemy SDK, the easiest and most powerful way to access the blockchain and Alchemy's suite of enhanced APIs.

If you have an existing client such as Web3.js or Ethers.js, you can just change your current node provider URL to an Alchemy URL with your API key: https://eth-mainnet.alchemyapi.io/v2/your-api-key

Install the Alchemy SDK

To install the Alchemy SDK, you want to create a project, and then navigate to your project directory to run the installation. Let's go ahead and do that! Once we're in our home directory, let's execute the following:

With Yarn:

mkdir your-project-name
cd your-project-name
yarn init # (or yarn init --yes)
yarn add alchemy-sdk

With NPM:

mkdir your-project-name
cd your-project-name
npm init   # (or npm init --yes)
npm install alchemy-sdk

Create index.js

import { Alchemy, Network } from "alchemy-sdk";

const settings = {
  apiKey: "demo", // Replace with your Alchemy API key.
  network: Network.ETH_MAINNET, // Replace with your network.
};

const alchemy = new Alchemy(settings);

async function main() {
  const gasPrice = await alchemy.core.getGasPrice();
  console.log(gasPrice.toString());
}

main();

Run

node index.js