Node SDK (HCS17Client)

The Node client publishes and verifies HCS‑17 state hashes using an operator account. It centralizes topic creation and message submission while delegating all transaction construction to tx.ts.

Setup

import { HCS17Client } from '@hashgraphonline/standards-sdk';

const client = new HCS17Client({
  network: 'testnet',
  operatorId: process.env.ACCOUNT_ID!,
  operatorKey: process.env.PRIVATE_KEY!, // string or PrivateKey
  keyType: 'ed25519', // or 'ecdsa' if needed
  logLevel: 'info',
});

Create a State Topic

Topics for HCS‑17 messages must use the numeric memo format hcs-17:<type>:<ttl>.

const topicId = await client.createStateTopic({
  ttl: 86400,
  // adminKey/submitKey can be boolean | string | PublicKey | KeyList
});

The client validates memo structure via parseHCS17Memo and exposes validateHCS17Topic(topicId) if you need to verify existing topics.

Submit a Message

If you already have a computed state hash and topic list, build a valid payload and submit:

import { StateHashMessage } from '@hashgraphonline/standards-sdk';

const message: StateHashMessage = client.createStateHashMessage(
  'abc123…',              // stateHash
  '0.0.1234',             // accountId
  ['0.0.2001','0.0.2002'],// topics
  'optional memo',        // m
);

await client.submitMessage(topicId, message);

Compute and Publish

The high‑level helper fetches latest running hashes from Mirror Node, computes the HCS‑17 account state hash, and publishes it to a target topic.

const { stateHash, receipt } = await client.computeAndPublish({
  accountId: '0.0.1234',
  accountPublicKey: '302a30…', // or PublicKey
  topics: ['0.0.2001', '0.0.2002'],
  publishTopicId: topicId,
  memo: 'app context',
});

console.log('Published state hash:', stateHash);

Read Latest Messages

Mirror‑node helpers return parsed, schema‑validated HCS‑17 envelopes:

const recent = await client.getRecentMessages(topicId, { limit: 25, order: 'desc' });
const latest = await client.getLatestMessage(topicId);

Notes

• No dynamic imports are used; signing occurs with the configured operator.
• All transaction JSON is constructed in tx.ts builders (buildHcs17CreateTopicTx, buildHcs17MessageTx).
• Memos use numeric enums (HCS17TopicType.STATE = 0).