pubsub.js

A lightweight publish/subscribe server & client written in javascript.

The publish/subscribe model is perfect for making your web application appear real-time. Imagine several people all looking at the same page, when someone makes a change to the page it's instantly reflected to all other viewers of that page. This is pubsub.js!

A Channel is a group of subscribers all listening for publish, join, & leave events. Channels are created when needed and are destroyed when there are no subscribers.

A Client is a connection to the server from a web application that can be subscribed to any number of Channels.

pubsub.js is built with safety in mind. All data sent to the server is validated before it creates channels, subscribes clients, or publishes to a channel.

Installing the Client

The easiest way to install pubsub.js is through bower via bower install clickermonkey-pubsubjs

Installing the Server

npm install clickermonkey-pubsubjs

Running the Server

node node_modules/clickermonkey-pubsubjs/pubsub-server.js path/to/my/config.js

Client Code

var pubsub = new PubSub('http://localhost:3000');
var channel = pubsub.subscribe('channel ID', 'user token');
channel.onpublish = function(data) {
  console.log('data received:', data);
};
channel.onjoin = function(userToken) {
  console.log('user join:', userToken);
};
channel.onleave = function(userToken) {
  console.log('user leave:', userToken);
};
channel.publish('Hello World!');
channel.unsubscribe();

(see examples/chat.html for a chat demo)

Configuration (config.js)

{
  /**
   * The port the application listens on.
   */
  port: 3000,

  /**
   * Whether or not to send a publish message back to the client who sent it.
   */
  echoPublish: false,

  /**
   * If this server should notify clients when other clients have joined or left
   * a channel. The client's token it used to subscribe is sent along with these
   * notifications so the client can identify them. If this is set to false
   * then tokens are ignored altogether in the system.
   */
  sendJoinLeaveEvents: true,

  /**
   * The maximum number of channels that can be created.
   */
  maxChannels: -1,

  /**
   * The maximum number of clients that may connect.
   */
  maxClients: -1,

  /**
   * If a client has sent an invalid channel ID, join token, or publish data
   * this determines whether the client is marked untrused and is no longer
   * sent any messages.
   */
  ignoreInvalidClients: true,

  /**
   * The number of previous publishes to keep and send to a client when they join.
   */
  sendLastPublishesOnJoin: 10,

  /**
   * Whether or not to send all of the join tokens of current clients to the
   * new client when they first join the channel.
   */
  sendExistingClientsOnJoin: true,

  /**
   * Requires that a client must be subscribed to a channel before they can publish in it.
   */
  requireSubscription: true,

  /**
   * Logs events (comment out console.log to disable)
   */
  debug: function()
  {
    console.log.apply( console, arguments );
  },

  /****************************************************************************
   *                C H A N N E L    I D    V A L I D A T I O N
   ****************************************************************************/

  /**
   * The data types that are valid channel IDs.
   * If the id is found not to be valid, a channel will not be created.
   */
  validIds:
  {
    'number':     true,
    'string':     true,
    'boolean':    true,
    'object':     false,
    'undefined':  false
  },

  /**
   * A function which does further validation on a channel ID.
   * If the id is found not to be valid, a channel will not be created.
   */
  validateId: function(id)
  {
    var promise = new Promise( this );

    if ( this.validIds[ typeof id ] )
    {
      promise.$success();
    }
    else
    {
      promise.$failure();
    }

    return promise;
  },

  /****************************************************************************
   *             C L I E N T    T O K E N    V A L I D A T I O N
   ****************************************************************************/

  /**
   * The data types that are valid client tokens.
   * If a token is found to be not valid, the user does not join the channel.
   */
  validTokens:
  {
    'number':     true,
    'string':     true,
    'boolean':    true,
    'undefined':  true,
    'object':     false
  },

  /**
   * A function which does further validation on a client token.
   * If a token is found to be not valid, the user does not join the channel.  
   */
  validateToken: function(token)
  {
    var promise = new Promise( this );

    if ( this.validTokens[ typeof token ] )
    {
      promise.$success();
    }
    else
    {
      promise.$failure();
    }

    return promise;
  },

  /****************************************************************************
   *                 P U B L I S H    V A L I D A T I O N
   ****************************************************************************/

  /**
   * The data types that are valid to publish to other clients.
   */
  validPublish:
  {
    'number':     true,
    'string':     true,
    'boolean':    true,
    'undefined':  true,
    'object':     true
  },

  /**
   * A function which validates if a message by a client can be published on a channel.
   */
  validatePublish: function(message, client, channel)
  {
    var promise = new Promise( this );

    if ( this.validPublish[ typeof message ] )
    {
      promise.$success();
    }
    else
    {
      promise.$failure();
    }

    return promise;
  }

}