Hedera Consensus Service (HCS) — JavaScript SDK

HCS provides a decentralized, ordered message log with consensus timestamps. It works like a pub/sub system: you create topics, submit messages to them, and subscribe to receive messages in real time via mirror nodes. Messages are immutable, ordered, and timestamped by network consensus — useful for audit trails, event logs, supply chain tracking, and decentralized communication.

Setup

All imports come from @hiero-ledger/sdk. Two setup patterns:

Client + setOperator (direct)

import { Client, AccountId, PrivateKey } from "@hiero-ledger/sdk";

const client = Client.forName(process.env.HEDERA_NETWORK)
    .setOperator(
        AccountId.fromString(process.env.OPERATOR_ID),
        PrivateKey.fromStringECDSA(process.env.OPERATOR_KEY),
    );