October 2012
Intermediate to advanced
408 pages
7h 35m
English
Content preview from Professional Node.js: Building Javascript Based Scalable SoftwareBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 22
Making Universal Real-Time Web Applications Using Socket.IO
WHAT’S IN THIS CHAPTER?
- Understanding the history of HTTP in relation to real-time applications
- Understanding how WebSockets enable real-time applications on the web
- Using Socket.IO to write real-time applications for Node.js
- Writing a web-based real-time chat with Socket.IO for Node.js
- Using namespaces to separate Socket.IO apps
- Scaling to several Node processes with Redis
For many years, HTTP and real-time applications didn’t really go together very well. The reason lies in the very nature of the HTTP protocol, which is stateless and based on a request-response cycle – an HTTP server only reacts upon requests from the client but doesn’t have a stateful continuous connection to the client.
An HTML and JavaScript-based application is capable of reacting to client events and sending them to the server, but the reverse is not easy. If an event on the server occurs, the server has no way of actively informing its clients about this event in real time. Only when clients ask the server for its current state can the information be delivered from the server to its clients.
A browser-based chat is a good example of a web-based real-time application that shows the limitations of HTTP. Multiple users share a chatroom, which technically means that a message sent by any of the participating users needs to be delivered to all other users in the same room.
To achieve real-time, or at least near real-time, behavior in traditional ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.