What the heck is Meteor DDP? - The Koch Family
The Koch Family The Koch Family

Latest news

جاري التحميل ...

What the heck is Meteor DDP?




I was using Meteor for my messenger project. I was so curious about the real time connection. I wanted to know how exactly this mechanism works. In this post, I will go through the DDP Specification, an overview of WebSocket, and a simple demo about how to subscribe a publication of Rocket.Chat (containing a DDP server) from an external webpage.

At a glance, I knew that Meteor invented a protocol called DDP which uses for handling real time connection. So then, what is DDP?

"DDP (Distributed Data Protocol) is the stateful WebSocket protocol that Meteor uses to communicate between the client and the server." [1]

All right! Why does DDP matter?

"DDP is a standard way to solve the biggest problem facing client-side JavaScript developers: querying a server-side database, sending the results down to the client, and then pushing changes to the client whenever anything changes in the database". [2]

In order to understand deeply the protocol, I decided to explore its specification, and then took a look at its implementation.

The Specification

The official specification is easily found here. It is quite simple! I tried to draw a diagram (sequence-liked) to visualize its flow.

The Implementation

As its definition, DDP is a WebSocket protocol. Hence, I needed to understand WebSocket protocol as well. A normative way to learn a protocol is to read it RFC. The WebSocket Protocol is specified under RFC-6455. After that, I followed to implement a WebSocket server with Node.js. I was able to understand how WebSocket protocol works.
Then, I took a look into some implementations of DDP available on the net. Here was an example:
I tried to simplify an implementation of DDP by writing a pseudo code as below:

Practice

Assignment: “Obtaining Active Users of Rocket.Chat instance for a webpage in real time

As my understanding so far, I needed to use WebSocket with DDP, so that I could:
- Maintain real time connection via WebSocket
- Communicate with Meteor via DDP

With node-ddp-client, I could make a connection with DDP server of Meteor, but the implementation was only in server side. I decided to implement a similar stuff, but in client side, which can be executed in browsers.

Check out my project here

------------
Reference:

[1]. https://github.com/meteor/meteor/tree/devel/packages/ddp
[2]. https://blog.meteor.com/introducing-ddp-6b40c6aff27d?gi=65983e20e448
[3]. https://hackernoon.com/implementing-a-websocket-server-with-node-js-d9b78ec5ffa8
[4]. https://github.com/hharnisc/node-ddp-client

Comments



If you like the content of our blog, we hope to stay in constant communication, just enter your email to subscribe to the blog's express mail to receive new blog updates, and you can send a message by clicking on the button next ...

إتصل بنا

About the site

author The Koch Family <<  Welcome! I'm so glad that you stopped by Your Modern Family blog. Together, we will talk about raising kids, organizing the home and saving money! and Tips & tricks and more…

< Learn more ←

Blog stats

Sparkline 2513183

All Copyrights Reserved

The Koch Family

2020