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WebSockets overview

From: HTML5 First Look

Video: WebSockets overview

Another specification that was originally part of the HTML5 specification and then split off later is the WebSocket API. Describing what the WebSocket API is, is rather difficult without first discussing how clients and servers have communicated in the past. At first, the web was stateless. The client would send a request to the server; the server would process it and then send back the requested information. Now, usually that would refresh the page. Now, much of the web still works this way today.

WebSockets overview

Another specification that was originally part of the HTML5 specification and then split off later is the WebSocket API. Describing what the WebSocket API is, is rather difficult without first discussing how clients and servers have communicated in the past. At first, the web was stateless. The client would send a request to the server; the server would process it and then send back the requested information. Now, usually that would refresh the page. Now, much of the web still works this way today.

Over time more sophisticated means of sending data back and forth to the server evolved. AJAX applications are able to send data asynchronously, retrieving the data from a server without requiring a page refresh. Now, Comet is a term that's used to describe the technique of sending data from the server without necessarily requiring a request from the browser. Both of these techniques allow developers to create much more dynamic, responsive and user-friendly applications. At their core however, they both have problems.

In the end these techniques still require the client to initiate the request. If data changes on the server, there is no way for the client to know or even respond to this. Comet applications get around this by something called long polling, where the Browser sends a request to the server and the server keeps that request open for a set amount of time. As you could imagine these techniques can put a large amount of strain on the server and forces the server to keep track of these polling requests. What's more, the techniques required for AJAX and Comet applications to deal with firewalls and proxy servers can be mind-numbingly complex.

Well, this is where WebSockets come in. The WebSocket API is designed to create a single bidirectional connection between the client and server. Unlike AJAX or Comet solutions WebSockets are designed to be native to the Browser making them lightweight and easy to implement. Perhaps more importantly, WebSockets use their own protocol, allowing them to tunnel through firewalls and proxies with no additional effort. WebSockets work by opening up an HTTP connection to the server and then negotiating a persistent WebSocket connection using either the WebSocket or secure WebSocket protocol.

Now, you can see here how simple the syntax is for establishing a WebSocket connection. Once the connection is established there are methods available to control sending the data and monitoring the connection. The use of WebSockets will provide immediate benefits for web applications. First, since firewalls and proxies are no longer problematic streaming is now possible through any connection. Since the connections are bidirectional, separate connections for upstream and downstream communications aren't necessary.

Essentially cutting the number of connections required by your server in half. Also WebSockets can be used by any client, essentially meaning they can be used with AIR clients, Flash, Flex and Silverlight. The WebSocket specification only defines support for JavaScript, but I promise you that as it matures you'll see many third-party solutions for using them with other binary protocols. That sounds great, right? So, why isn't everybody using them? Well, they're not fully supported yet in most browsers. As you can see, only Chrome, Firefox, and Safari support native WebSockets and full support throughout modern browsers could take some time.

If you're interested in learning more about Web Sockets, check out the W3 specification for both the Web Socket API and the Web Socket protocol. I also recommend checking out jWebSocket. jWebSocket is an open-source Java and JavaScript implementation of the WebSocket protocol, with many improvements and extensions. The site monitors browser implementation and features a lot of guides and tutorials. Even though the implementation of WebSockets is not as far long as some of the other APIs, this specification, perhaps more than any other, is going to change the way web applications are created and what they are capable of.

I recommend keeping a close eye on the development of WebSockets and how their adoption will change the web.

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This video is part of

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HTML5 First Look

50 video lessons · 75147 viewers

James Williamson
Author

 
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  1. 3m 56s
    1. Welcome
      1m 1s
    2. Using the exercise files
      1m 50s
    3. Who is this course for?
      1m 5s
  2. 21m 12s
    1. Exploring prior standards
      4m 26s
    2. Why do we need HTML5?
      3m 32s
    3. HTML5 timeline
      4m 24s
    4. Current HTML5 support
      4m 25s
    5. What HTML5 is (and what it isn't)
      4m 25s
  3. 27m 49s
    1. HTML5 vs. HTML4
      3m 25s
    2. New structural tags
      6m 1s
    3. New content tags
      4m 7s
    4. New application-focused tags
      5m 32s
    5. Deprecated elements
      4m 28s
    6. API overview
      4m 16s
  4. 22m 29s
    1. Content models
      5m 33s
    2. Understanding the outline algorithm
      3m 21s
    3. The role of ‹div› tags
      4m 20s
    4. Using ID and class attributes
      2m 6s
    5. DOCTYPE declarations
      4m 16s
    6. Character encoding
      2m 53s
  5. 41m 27s
    1. Basic page structure
      3m 40s
    2. Structuring top-level elements
      7m 30s
    3. Structuring interior content
      8m 42s
    4. Building headers
      9m 11s
    5. Checking document outlines
      5m 46s
    6. Ensuring cross-browser structure
      6m 38s
  6. 27m 53s
    1. New input types
      5m 57s
    2. Setting form autofocus
      2m 53s
    3. Using placeholder data
      4m 4s
    4. Marking required fields
      3m 24s
    5. Working with number inputs
      5m 49s
    6. Using date pickers
      5m 46s
  7. 1h 1m
    1. Canvas overview
      6m 21s
    2. Adding canvas content
      8m 58s
    3. Drawing in the canvas environment
      12m 9s
    4. Drag-and-drop API overview
      6m 18s
    5. Offline applications overview
      7m 11s
    6. Video overview
      5m 45s
    7. Encoding video
      8m 23s
    8. Adding video
      5m 58s
  8. 57m 33s
    1. Geolocation API overview
      5m 50s
    2. Web storage API overview
      5m 40s
    3. WebSockets overview
      4m 16s
    4. CSS3 overview
      6m 38s
    5. Enhancing typography with CSS3
      7m 42s
    6. Using @font-face
      7m 11s
    7. Styling HTML5 with CSS3
      10m 23s
    8. Using CSS3 transitions
      9m 53s
  9. 5m 6s
    1. Final thoughts
      3m 49s
    2. Goodbye
      1m 17s

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