@polkadot/rpc-provider

Generic transport providers to handle the transport of method calls to and from Polkadot clients from applications interacting with it. It provides an interface to making RPC calls and is generally, unless you are operating at a low-level and taking care of encoding and decoding of parameters/results, it won't be directly used, rather only passed to a higher-level interface.

Provider Selection

There are three flavours of the providers provided, one allowing for using HTTP as a transport mechanism, the other using WebSockets, and the third one uses substrate light-client through @substrate/connect. It is generally recommended to use the [[WsProvider]] since in addition to standard calls, it allows for subscriptions where all changes to state can be pushed from the node to the client.

All providers are usable (as is the API), in both browser-based and Node.js environments. Polyfills for unsupported functionality are automatically applied based on feature-detection.

Usage

Installation -

yarn add @polkadot/rpc-provider

WebSocket Initialization -

import { WsProvider } from '@polkadot/rpc-provider';

// this is the actual default endpoint
const provider = new WsProvider('ws://127.0.0.1:9944');
const version = await provider.send('client_version', []);

console.log('client version', version);

HTTP Initialization -

import { HttpProvider } from '@polkadot/rpc-provider';

// this is the actual default endpoint
const provider = new HttpProvider('http://127.0.0.1:9933');
const version = await provider.send('chain_getBlockHash', []);

console.log('latest block Hash', hash);

@substrate/connect Initialization -

Instantiating a Provider for the Polkadot Relay Chain:

import { ScProvider } from '@polkadot/rpc-provider';
import * as Sc from '@substrate/connect';

const provider = new ScProvider(Sc, Sc.WellKnownChain.polkadot);

await provider.connect();

const version = await provider.send('chain_getBlockHash', []);

Instantiating a Provider for a Polkadot parachain:

import { ScProvider } from '@polkadot/rpc-provider';
import * as Sc from '@substrate/connect';

const polkadotProvider = new ScProvider(Sc, Sc.WellKnownChain.polkadot);
const parachainProvider = new ScProvider(Sc, parachainSpec, polkadotProvider);

await parachainProvider.connect();

const version = await parachainProvider.send('chain_getBlockHash', []);