meteor.js + DDP + webSockets + Objective-C

Its an introductory blog post which aims at projecting an overview of all the above technologies and how they can be used together.

Introduction #

Meteor is an open-source JavaScript platform for building web apps.

http://docs.meteor.com/ #

Installation:

[curl https://install.meteor.com | /bin/sh]

First Project:

meteor create ~/myapp
cd ~/myapp
meteor

Notes:

• it saves the scripts at /usr/local/bin/meteor
• it uses MongoDB for database
• it uses DDP for client-server communication.
• for indepth reading core features/implementations of Meteor
• for 3rd party meteor modules, we have Atmosphere
• to manage 3rd party modules we have to use Meteorite
• Our JavaScript code can run in two environments: the client (browser), and the server (a Node.js container on a server).

http://meteorhacks.com/introduction-to-ddp.html #

DDP - Distributed Data Protocol

• Meteor uses it to communicate between the client and the server
• It is a protocol based on JSON
• Meteor’s current implementation is based on WebSockets and SockJS
• SockJS is a WebSockets emulation transport, which can be used when WebSockets is not available.

What DDP do ?

• it handles RPCs (Remote Procedural Calls)
• it manages data

RPC

• 3 step process
  • request (aka methods)
  • result
  • update

Managing Data

• A client can use it to subscribe into a real-time data source and get notifications.
• The DDP protocol has three types of notification: added, changed and removed.
• Since the DDP protocol was inspired by MongoDB, each data notification (a JSON object) is assigned to a collection, which is the place where the data belongs.

https://www.meteor.com/blog/2012/03/21/introducing-ddp #

More stuff on DDP

• On the server, you define a realtime queries using Meteor.publish. You can publish data from any source.
• On the client, you call Meteor.subscribe to connect to a publication endpoint, receive the data, and listen for updates. The data is inserted directly into Meteor’s client-side cache, so you can bind your HTML templates to it and they’ll update automatically.

WebSockets #

Introduction

• it makes it possible to open an interactive communication session between the user’s browser and a server.
• With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply.

further reading #

• Meteor
• DDP
• ObjectiveDDP
• official websockets doc
• Mozilla websockets basics
• html5rocks websockets basics
• Objective-C WebSocket client library.