Query a node with JSON-RPC

First prepare a node with leani init blocks and leani serve as described in Getting started. Its JSON-RPC endpoint is http://127.0.0.1:18545; its separate native SDK API is on port 18080.

Check the chain

curl -s http://127.0.0.1:18545 \
  -H 'Content-Type: application/json' \
  --data '{"jsonrpc":"2.0","id":1,"method":"eth_chainId","params":[]}'

Expect {"jsonrpc":"2.0","id":1,"result":"0x1"} for Ethereum Mainnet.

In a Bun application, install viem with bun add viem, save the following as watch.ts, and run bun watch.ts:

import { createPublicClient, http } from "viem";

const eth = createPublicClient({
  transport: http("http://127.0.0.1:18545"),
});
console.log(await eth.getChainId()); // 1

Requesting blocks, receipts, or state

Available data depends on the node’s configured sources and retained material. The block-summary feed requests headers and bodies without receipts. A historical receipts request needs a source that supplies complete receipts; the filtered Xatu event quickstart alone cannot satisfy it and returns no_viable_historical_source.

The full historical configuration examples use RPC port 8545. Use the rpc_http listener shown by leani doctor --json for your selected profile. Do not infer the port or supported data from a different tutorial.

See the RPC method matrix before moving an existing application. Arbitrary eth_call, account-state queries, and execution simulation are outside the EVM-free core.