@steelbreeze/broker/README.md

Lightweight publish and subscribe using Server-Sent Events for node and express

# broker
Lightweight publish and subscribe using Server-Sent Events for node and express

If you like broker, please star it...

## Install
```shell
npm i @steelbreeze/broker
```
## Usage
### Server
To create a message broker server within an express application:
```javascript
const express = require('express');
const broker = require('@steelbreeze/broker');

// create the express application
var app = express();

// create a message broker that provides the last message on subscription
var events = broker.server({lastMessage: true});

// bind the message broker to the /events base URL
app.use('/events', events);

// start the express application
app.listen(1024, 'localhost');
```
You can create multiple message broker servers and bind them to different base URLs in the same express application.
### Subscriber (node)
To create a subscription:
```javascript
const broker = require('@steelbreeze/broker');

// create a client to the message broker
var client = broker.client({host:'localhost', port: 1024, path: '/events'});

// subscribe to the devices topic on the /events broker
client.subscribe('devices', (message) => {
	console.log(`All devices: (${message.id}) ${message.data}`);
});
```
A single client can subscribe to multiple topics.
### Publisher (node)
To create a subscription:
```javascript
const broker = require('@steelbreeze/broker');

// create a client to the message broker
var client = broker.client({host:'localhost', port: 1024, path: '/events'});

// publish a message on the devices topic of the /events broker every second
var timer = setInterval( () => {
	client.publish('devices', `Hello at ${new Date()}`, onError);
}, 1000);

function onError() {
	clearInterval(timer);
}
```
### Web clients
In addition to using the provided client, a browser's ```EventSource``` may be used to subscribe and an HTTP POST can be used to publish.
> Note: for some browsers this may require an EventSource polyfill.
## License
MIT License

Copyright (c) 2018 David Mesquita-Morris