# monero-lws ZeroMQ Usage
Monero-lws uses ZeroMQ-RPC to retrieve information from a Monero daemon,
ZeroMQ-SUB to get immediate notifications of blocks and transactions from a
Monero daemon, and ZeroMQ-PUB to notify external applications of payment_id
(web)hooks.

## External "pub" socket
The bind location of the ZMQ-PUB socket is specified with the `--zmq-pub`
option. Users are still required to "subscribe" to topics:
  * `json-full-pyment_hook`: A JSON array of webhook payment events that have
    recently triggered (identical output as webhook).
  * `msgpack-full-payment_hook`: A msgpack array of webhook payment events that
    have recently triggered (identical output as webhook).


### `json-full-payment_hook`/`msgpack-full-payment_hook`
These topics receive PUB messages when a webhook ([`webhook_add`](administration.md)),
event is triggered. If the specified URL is `zmq`, then notifications are only
done over the ZMQ-PUB socket, otherwise the notification is sent over ZMQ-PUB
socket AND the specified URL. Invoking `webhook_add` with a `payment_id` of
zeroes (the field is optional in `webhook_add), will match on all transactions
that lack a `payment_id`.

Example of the "raw" output from ZMQ-SUB side:

```json
json-full-payment_hook:{
  "index": 2,
  "event": {
    "event": "tx-confirmation",
    "payment_id": "4f695d197f2a3c54",
    "token": "single zmq wallet",
    "confirmations": 1,
    "event_id": "3894f98f5dd54af5857e4f8a961a4e57",
    "tx_info": {
      "id": {
        "high": 0,
        "low": 5666768
      },
      "block": 2265961,
      "index": 1,
      "amount": 3117324236131,
      "timestamp": 1687301600,
      "tx_hash": "ef3187775584351cc5109de124b877bcc530fb3fdbf77895329dd447902cc566",
      "tx_prefix_hash": "064884b8a8f903edcfebab830707ed44b633438b47c95a83320f4438b1b28626",
      "tx_public": "54dce1a6eebafa2fdedcea5e373ef9de1c3d2737ae9f809e80958d1ba4590d74",
      "rct_mask": "4cdc4c4e340aacb4741ba20f9b0b859242ecdad2fcc251f71d81123a47db3400",
      "payment_id": "4f695d197f2a3c54",
      "unlock_time": 0,
      "mixin_count": 15,
      "coinbase": false
    }
  }
}

```

Notice the `json-full-payment_hook:` prefix - this is required for the ZMQ PUB/SUB
subscription model. The subscriber requests data from a certain "topic" where
matching is done by string prefixes.

> `index` is a counter used to detect dropped messages.

> The `block` and `id` fields in the above example are NOT present when
`confirmations == 0`.