Publish doesn't send messages

[losnappas]

Hi,

I don't think the publish is working correctly.

const nknWallet = require('nkn-wallet')
const nkn = require('nkn-client')
const wallet = nknWallet.newWallet('pwd')
const client = nkn({
  privateKey: wallet.getPrivateKey(),
  indentifier: 'client'
})
const receivingClientWallet = nknWallet.newWallet('pwd')
receivingClientWallet.subscribe(
	'topic',
	0,
	10,
	'pwd',
	'identifier'
)
client.on('connect' , () => 
setTimeout(() => {
	client.publish(
	'topic',
	0,
	'hello world'
	)
}, 1000)
)

This makes a request where it gets a result like {"id":"1","jsonrpc":"2.0","result":{"identifier.02c988e6a672fd6b8cf42e68682362ee152a8afb5176b9206c558b4cb89daba47d":"","identifier.0352304707e0af0187b435ea5f3ec8f3a0fbac71e3e801dbc34b3cf8d4000d1128":"","identifier.03c7575885c10f141576d817fa5fbca5144e74e3fd85838530ec8a8027d587aa5a":""}}

But then nothing gets sent to them afterwards. My understanding was that it is a shortcut to send the message to all those addresses automatically.

[yilunzhang]

Yes your understanding is correct, but subscribe takes some time (usually less than one block interval, i.e. 20s) to be effective because it is an on-chain operation (that's why it's in wallet). publish is an off-chain operation, so once subscriber info is recorded on-chain, publish will be instant

[losnappas]

I don't see any messages getting sent even when the response result field has entries, though. I.e. if I change to a 30sec timeout in my example there, although it does find the subscriber in the response, it still never sends any messages.

On a related note, could you please set the publish method to return the response object, instead of nothing.

[yilunzhang]

You are right, recently metadata is added to subscriber info so it's not parsing correctly. It's fixed in #47 now. Here is a working example:

const nknWallet = require('nkn-wallet')
const nknClient = require('nkn-client')

const sendingClient = nknClient()

const receivingWallet = nknWallet.newWallet('pwd');
const receivingClient = nknClient({
  privateKey: receivingWallet.getPrivateKey(),
  identifier: 'client'
})

receivingWallet.subscribe('topic', 0, 10, 'pwd', receivingClient.identifier).then(r => {
  console.log('subscribe success:', r)
})

receivingClient.on('message', (src, payload) => {
  console.log('reveive message:', payload)
})

sendingClient.on('connect', () => {
  setTimeout(() => {
    console.log('publish');
    sendingClient.publish('topic', 0, 'hello world')
  }, 60 * 1000);
})

60s is usually enough, but in some cases it may take longer because the txn may be packed in a later block, plus block interval can be increased from 20s to 60s in some cases.

Publish is a one-to-many message and thus does not support reply, otherwise it may be used to perform DDoS attack. It may throw error though.

[losnappas]

Yeah, it works now, but it also has a bug. The rpcCall function doesn't seem to always throw errors, instead it returns them.

// rpc.js
module.exports = rpcCall;

async function rpcCall(addr, method, params = {}) {
  let response = await fetch(addr, {
    method: 'POST',
    body: JSON.stringify({
      jsonrpc: "2.0",
      method: method,
      params: params,
    }),
  })
  let data = await response.json();
  return data;
}

So sometimes it returns

{
  error: { code: -42002, message: "INVALID PARAMS" },
  id: "1",
  jsonrpc: "2.0",
}

And then I get TypeError: "can't convert undefined to object" because it calls Object.keys on res.result which is obviously undefined.

You can test it like this

sendingClient.on('connect', () => {
  setTimeout(() => {
    console.log('publish');
    sendingClient.publish(null, 0, 'hello world') // null topic is illegal
  }, 60 * 1000);
})

But this wasn't a bug in the code, but a mistake on my part, huh. so it works correctly now, I guess.

[yilunzhang]

Fixed in #49 (in ed25519 branch instead of master though)