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Primus Multiplex

Node.JS module that adds mutiplexing to Primus.

Installation

$ npm install primus-multiplex

Usage

On the Server

var Primus = require('primus');
var multiplex = require('primus-multiplex');
var server = require('http').createServer();

// primus instance
var primus = new Primus(server, { transformer: 'sockjs', parser: 'JSON' });

// add multiplex to Primus
primus.plugin('multiplex', multiplex);

var news = primus.channel('news');
news.on('connection', function (spark) {

  spark.write('hi from the news channel');

  spark.on('data', function (data) {
    spark.write(data);
  });

});

var sport = primus.channel('sport');
sport.on('connection', function (spark) {

  spark.write('hi from the sport channel');

  spark.on('data', function (data) {
    spark.write(data);
  });

});

server.listen(8080);

On the Client

var primus = Primus.connect('ws://localhost:8080');

// Connect to channels
var news = primus.channel('news');
var sport = primus.channel('sport');

// Send message
news.write('hi news channel');
sport.write('hi sport channel');

// Receive message
news.on('data', function (msg) {
  console.log(msg);
});
sport.on('data', function (msg) {
  console.log(msg);
});

API

Server

primus.channel(name)

Create a new channel on the server.

var news = primus.channel('news');
news.on('connection', fn);

channel.write(message)

Broadcast a message to all connected Sparks in the channel.

news.write(message);

channel.forEach(fn)

Iterare over all Sparks in a channel. This could also be used for broadcasting to specific Sparks.

news.forEach(function (spark, id, connections) {
  spark.write('message');
});

channel.destroy()

Destroy the channel removing all 'Sparks' and event listeners. This will emit a close event.

news.on('connection', function (spark) {
  news.destroy();
});

channel.on('close', fn)

Triggers when the destroy method is called.

news.on('connection', function (spark) {
  news.destroy();
});

news.on('close', function () {
  console.log('channel was destroyed');
});

spark.end([fn])

End the connection.

news.on('connection', function (spark) {
  spark.end(fn);
});

Client

channel.write(message)

Send a message to the server.

news.write('hi server');

channel.end()

Disconnect from a channel.

var news = primus.channel('news');
news.end();

channel.on('data', fn)

Receive data from the server from the corresponding channel.

news.on('data', function(msg) {
  console.log('Received message from news channel', msg);
});

Events on main Spark (Server)

There are two useful events that will be triggered on the main primus Spark object, that can be very usefull for handling dynamic subscriptions, subscription notifications, etc.

spark.on('subscribe', fn)

Triggers when a connection is subscribed to a channel. Callback will return with channel object and its spark object.

primus.on('connection', function(spark) {
  spark.on('subscribe', function(channel, channelSpark) {
    console.log('spark %s subscribed to channel %s', channelSpark.id, channel.name);
    // do stuff with the channel spark
  });
});

spark.on('unsubscribe', fn)

Triggers when connection is unsubscribed from a channel. Callback will return the channel object and its spark object.

primus.on('connection', function(spark) {
  spark.on('unsubscribe', function(channel, channelSpark) {
    console.log('spark %s unsubscribed from channel %s', channelSpark.id, channel.name);
    // channel spark is about to die
  });
});

Protocol

Each message consists of an array of four parts: type (Number), id (String), topic (String), and payload (Mixed).

There are three valid message types:

Packet#MESSAGE (0) send a message with payload on a topic.
Packet#SUBSCRIBE (1) subscribe to a given topic.
Packet#UNSUBSCRIBE (2) unsubscribe from a topic.

The topic identifies a channel registered on the server side. The id represent a unique connection identifier generated on the client side.

Each request to subscribe to a topic from a given client has a unique id. This makes it possible for a single client to open multiple independent channel connection to a single server-side service.

Invalid messages are simply ignored.

It's important to notice that the namespace is shared between both parties and it is not a good idea to use the same topic names on the client and on the server side. Both parties may express a will to unsubscribe itself or other party from a topic.

Run tests

$ make test

Inspiration

This library was inspire by this great post:

https://www.rabbitmq.com/blog/2012/02/23/how-to-compose-apps-using-websockets/

Other plugins

PrimusMultiplex is compatible with the following plugins, check the examples to see more.

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.