Verus ZMQ Client

An intuitive and lightweight Typescript/Javascript client library for the Verus Coin ZMQ messaging.

Introduction

Verus ZMQ Client is a library that enables to receive event notification from the Verus blockchain nodes via ZeroMQ (ZMQ) messaging protocol.
This library provides functionalities to subscribe to various types of blockchain data events and receive real-time updates.

Verus Coin Setup

To receive the events from the Verus blockchain, you need to enable the ZMQ setting first by adding the following lines in the VRSC.conf.

📑 Note
You should have a Verus node running locally.
The address 127.0.0.1:8900 will serve as the ZMQ web server to be accessed by this library. You can change it to any available ports.

OS	Directory
	~/.komodo/VRSC
	/Users//Library/Application Support/komodo/VRSC
	%AppData%\Komodo\VRSC\

Steps

This is applicable for Verus and PBaaS blockchains.

1. Update the configuration file (see below).
2. Restart the node.

ZMQ Configuration

Copy and paste to the config file.

...
zmqpubrawblock=tcp://127.0.0.1:8900
zmqpubrawtx=tcp://127.0.0.1:8900
zmqpubhashtx=tcp://127.0.0.1:8900
zmqpubhashblock=tcp://127.0.0.1:8900

⛓ PBaaS Chain Ready

PBaaS is already supported by this library. To enable, just follow the same setup procedure.
Ideally, the port should be different from the Verus node ZMQ configuration.

Take note that PBaaS chain configurations (*.conf file) are located in a directory different from Verus.
For example, in Linux, can be found in ~/.verus/pbaas/<pabaas_chain_id>/<pabaas_chain_id>.conf

🔖see for more details

Installation

To install, you can use npm:

npm install verus-zmq-client

Usage

Importing the Library

import {
    EventData,
    SubscriptionEventsHandler,
    SubscriptionTopics,
    VerusZmqClient,
    VerusZmqConnection,
    VerusZmqOptions
} from 'verus-zmq-client';

Example

const eh: SubscriptionEventsHandler = {
    onRawTxReceived: function (value: EventData): Object {
        console.log("onRawTxReceived >> " + value);
        return {};
    },
    onHashTxReceived: function (value: EventData): Object {
        console.log("onHashTxReceived >> " + value);
        return {};
    },
    onRawBlockReceived: function (value: EventData): Object {
        console.log("onRawBlockReceived >> " + value);
        return {};
    },
    onHashBlockReceived: function (value: EventData): Object {
        console.log("onHashBlockReceived >> " + value);
        return {};
    },
    before: function(value: EventData, topic?: string) {
        console.log(`before value >> ${value} ${topic}`);
        return {};
    },
    after: function(value: EventData, topic?: string) {
        console.log(`after value >> ${value} ${topic}`);
    }
};

const zmqClient = new VerusZmqClient(
    new VerusZmqOptions(
        new VerusZmqConnection(
            '127.0.0.1',
            8900,
            [
                SubscriptionTopics.rawTx,
                SubscriptionTopics.hashTx,
                SubscriptionTopics.rawBlock,
                SubscriptionTopics.hashBlock,
            ],
            eh
        )
);

try {
    zmqClient
        .connect()
        .listen();
} catch (e) {
    console.error('Error: ' + e)
}

// Don't forget to disconnect
// zmqClient.disconnet()

API

VerusZmqClient Class

Main client class for connecting to the Verus node ZMQ server.

Methods

Name	Usage
connect	connects to the Verus ZMQ server
listen	starts listening to the stream of events
disconnect	disconnects from the Verus ZMQ server

VerusZmqOptions Class

Main configuration class of the VerusZmqClient class.

Topics

Topics are optional. Just subscribe to the topics you need by using the following SubscriptionTopics enums.

Name	Verus ZMQ Topic
SubscriptionTopics.rawTx	rawtx
SubscriptionTopics.hashTx	hashtx
SubscriptionTopics.rawBlock	rawblock
SubscriptionTopics.hashBlock	hashblock

Event Handlers

Event handlers are optional. They are dependent to the subscribed topics.
Define the event handlers you need.

Name	Trigger
onRawTxReceived	✅ notifies about all transactions, both when they are added to mempool or when a new block arrives. ✅ receives the transaction information
onHashTxReceived	✅ notifies about all transactions, both when they are added to mempool or when a new block arrives. ✅ receives the transaction information hash
onRawBlockReceived	✅ notifies when the chain tip is updated. ✅ receives the block information
onHashBlockReceived	✅ notifies when the chain tip is updated. ✅ receives the block information hash
before	✅ called before the actual ZMQ event is being handled. ✅ this receives the raw message and the topic received from the chain. ✅ raw means, it can either be a Buffer object or a string as it's not yet processed. ✅ the return value will be passed as an optional third argument of the main events. i.e.. onRawTxReceived(value: EventData, topic?: string, beforeResult?: Object)
after	✅ called after the actual ZMQ main event is being handled. ✅ the third parameter will be the return value of the main event called.

📑 Note
Processing of the main (on*Received), before and after events can be think of like the following.

before ➜ onRawTxReceived ➜ after
before ➜ onHashTxReceived ➜ after
before ➜ onRawBlockReceived ➜ after
before ➜ onHashBlockReceived ➜ after

---

Support

For any issues or inquiries, you can raise a PR or contact me at

Contacts	-
	Pangz#4102
	pangz.lab@gmail.com
	@Pangz55192569

Reference

• Verus : https://verus.io/
• Verus Wiki : https://wiki.verus.io/#!index.md
• Bitcoin ZMQ : https://github.com/bitcoin/bitcoin/blob/master/doc/zmq.md

License

This library is released under the MIT License.