Table of Contents

Core NATS

Core NATS is the base set of functionalities and qualities of service offered by a NATS service infrastructure. Core NATS is the foundation for JetStream and other services. For the sake of explanation, in a simplified sense you can think of Core NATS as the wire protocol defining a simple but powerful pub/sub functionality and the concept of Subject-Based Messaging.

Quick Start

Download the latest nats-server for your platform and run it without any arguments. nats-server will listen on its default TCP port 4222. You can also use a containerized version of the NATS server:

$ nats-server

or

$ docker run nats

Install NATS.Net from Nuget.

Given that we have a plain class Bar, we can publish and subscribe to our nats-server sending and receiving Bar objects:

public record Bar(int Id, string Name);

Subscribe to all bar related subjects:

await using var nc = new NatsClient();

await foreach (var msg in nc.SubscribeAsync<Bar>("bar.>"))
{
    if (msg.Subject == "bar.exit")
        break;

    Console.WriteLine($"Received {msg.Subject}: {msg.Data}\n");
}

Publish Bar objects to related bar subjects:

await using var nc = new NatsClient();

for (var i = 0; i < 10; i++)
{
    Console.WriteLine($" Publishing {i}...");
    await nc.PublishAsync<Bar>($"bar.baz.{i}", new Bar(Id: i, Name: "Baz"));
}

await nc.PublishAsync("bar.exit");

What's Next

Publish-Subscribe is the message distribution model for one-to-many communication.

Request-Reply is a common pattern in modern distributed systems. A request is sent, and the application either waits on the response with a certain timeout, or receives a response asynchronously.

Queue Groups enables the 1:N fan-out pattern of messaging ensuring that any message sent by a publisher, reaches all subscribers that have registered.

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