Replace your MQTT broker with NATS Server v2.2.0+

NATS Server v2.2.0+ has native support for MQTT v3.1.1 protocol.

If you already have a deployment with existing MQTT broker(s) and use NATS messaging, or are planning to, this blog post will show you how easy it is to replace your existing MQTT broker with a NATS server.

Not only you would have to manage a single server instead of two, using NATS with MQTT will allow you to exchange data from MQTT to NATS and vice-versa.

Java Client Usage on Android with Kotlin

Dependencies

To use the official NATS.java library in Android we need to add the dependency to the build.gradle file at Module level. Please use the latest released version, which at this writing is 2.11.2

dependencies {
    //other dependencies
    implementation 'io.nats:jnats:2.11.2'
}

Implementation

We will create a class as a manager to control our NATS client to be able to connect, disconnect, publish … This is necessary because when nats.java tries to connect, it makes a blocking call, which we don’t want in the main thread, so we execute it in another thread. Also, in order to have communication between the main thread and connect thread, we generate an interface that we will implement in the MainActivity and that we pass as parameter to our class NatsManager. In this case, we will make that the interface returns us when we are connected and what messages it revokes.

As we were building the NATS Java client we realized we wanted code to run the client through its paces. We built unit tests, example code and added basic functionality to our existing benchmarking tool.

As we talked to prospective users, they were asking for benchmarks across the variety of different ways we can publish and subscribe. For instance see publishing synchronous versus asynchronous. Push versus pull consuming. Different amounts of threading with shared or individual connections to the server. You get the idea. So we set out to build a tool to do just that.

Publish-Subscribe with NATS CLI

Previously we introduced the New NATS CLI , today we look at the Publish-Subscribe pattern using the CLI.

Links to related documentation:

• Subjects-Based Messaging
• Publish-Subscribe
• Queue Subscriptions
• Request-Reply
• The NATS CLI

About the Author

R.I. Pienaar is a long-time NATS Maintainer and a senior member of the engineering team at Synadia Communications .

Questions? Join our Slack channel or email info@nats.io .

Hello World with the NATS Java Library

Recently, stream functionality was added to the NATS server in release 2.2. See our JetStream section in docs for additional information.

Check out this video where I discuss the basics of how to create a stream and then publish and consume messages using the NATS Java client .

The full source of the project can be found here: https://github.com/nats-io/java-nats-examples/tree/main/hello-world

The previous entry in this series showed us how to create a stream. Once you have defined a stream, you can publish to the configured subjects. Publishing to stream subjects isn’t really much different from publishing a regular NatsMessage. Once a subject is established, you could publish a regular NatsMessage to that subject, but there are benefits to publishing via the JetStream API instead of the regular message API.

Publish Acknowledgement

When you publish via the JetStream API, each publish will receive an acknowledgement or PublishAck. This is the server’s way of letting you know it has received the message and has handled it according to the options like storage, retention and replication that were established when creating the stream.

The NATS Java library with support for JetStream has just been released!

JetStream allows you to persist streams of messages, allows consumers to either subscribe in real time or to access the messages at a later time with the added flexibility to choose from where in the stream you want to start receiving messages. You can start reading from the stream at a specific point in time or start at a specific message sequence number.

Introducing NATS CLI

Historically NATS did not have a clear obvious place to go for a CLI tool, users had various example applications that had to build and run manually. These tools were primarily examples of using the APIs rather than full UX CLI experience.

As part of the NATS 2.2.0 release that introduced JetStream and its administration needs, we took the opportunity to build a full CLI tool for users and administrators alike.

A few months ago, Header support was added to NATS Server. With the release of the 2.10.0 Java client , Headers are completely supported.

NATS Headers are analogous to http request Headers and you can leverage them for the same type of things, for example, to pass information like security, request, transaction or state information.

In Java terms, it’s analogous to a map of type

Map<String, List<String>>

In fact, that’s exactly what is used for the backing data structure in the Headers object. Using Headers is straightforward, again analogous to a Java map with some limitations to the keys and values.

Overview

NATS 2.2 is the largest feature release since version 2.0. The 2.2 release provides highly scalable, highly performant, secure and easy-to-use next generation streaming in the form of JetStream, allows remote access via websockets, has simplified NATS account management, and provides native MQTT support built into the server. These features further enables NATS toward our goal of securely democratizing streams and services for the hyperconnected world we live in.