HTML5 WebSocket is an important new technology that helps you build engaging, interactive, real-time web applications quickly and reliably. Sure, HTML5 WebSockets may be the best thing since sliced bread, but is this new technology right for you?

This article identifies five types of web applications that will benefit from HTML5 WebSockets. So, without further ado... give me five!

The Five Signs

1. Your web application has data that must flow bi-directional simultaneously.
2. Your web application must scale to large numbers of concurrent users.
3. Your web application must extend TCP-based protocols to the browser.
4. Your web application developers need an API that is easy to use.
5. Your web application must extend SOA over the Web and in the Cloud.

1. Your application has data that must flow bi-directional simultaneously.
When the Web was first conceived, it focused on document retrieval. Users requested a URL and the server delivered an object (for example, a web page or an image file). Today, the Web also comes to us. Servers want to let us know when they have something for us, be it a stock update or a message from a friend. Unfortunately, due to current Web architecture, clients must initiate communication with the server using half-duplex (request/response) HTTP. Even relatively static applications need a way to communicate asynchronously between the client and the server for common tasks, such as spell-checking or search auto-completion.

Up until now, in an effort to simulate full-duplex communication over half-duplex HTTP, developers have contrived clever tricks and techniques using two connections: one for the downstream and one for the upstream. Many of these techniques use polling or long-polling (Comet) to simulate server-initiated push. The maintenance and coordination of two connections causes significant resource consumption overhead and adds lots of complexity. Furthermore, these techniques do not provide true full-duplex communication where data can be transferred between the client and the server simultaneously. Simply put, HTTP was not designed for real-time, full-duplex communication.

Now, HTML5 WebSockets deliver a full-duplex communication model for the Internet: communication between the client and server can now flow in both directions at the same time. For today's web application developers, this new concept opens up entirely new application models without the burden and overhead of earlier approaches.

If you are building a web application that has data that must flow bi-directionally and simultaneously, you need to use HTML5 WebSockets.

2. Your application must scale to large numbers of concurrent users
If you are building a web application for a large number of concurrent users, you are inevitably going to face resource contention, particularly when each of your users must establish a connection to your back-end server. Typically, each of those connections includes the overhead of HTTP's verbose request-and-response protocol, as well as the establishment and teardown of secure connections.

The HTTP request and response model suffers from a significant amount of overhead. When retrieving a large document from a server, a few hundred bytes of HTTP header overhead is not a big deal. Consider what happens, however, when each message sent to a client is only a few bytes, such as a stock price update or a chat message that is only 20 characters long. The majority of the data transmitted in this case is unnecessary HTTP header overhead (up to 2000 or even more bytes for the single message), making the communication highly inefficient.

HTML5 WebSockets specify a new, vastly more efficient way of communicating between clients and servers that is far less taxing on the application and easier for the underlying network infrastructure to handle. Replacing hundreds of HTTP header bytes with just two WebSocket frame bytes leads to a massive reduction in unnecessary network throughput (1000:1). In addition, the lack of continuous polling dramatically reduces latency. All of this means that a single WebSocket server can deal with many more users at once, reducing the total cost of ownership (TCO).

HTML5 WebSockets provide such a dramatic improvement from the old, convoluted hacks that simulate a full-duplex connection in a browser that it prompted Google's Ian Hickson, the HTML5 specification lead, to say:

"Reducing kilobytes of data to 2 bytes... and reducing latency from 150ms to 50ms is far more than marginal. In fact, these two factors alone are enough to make WebSockets seriously interesting to Google."

3. Your application must extend TCP-based protocols to the browser.
Many web applications need to connect end users to information from back-end, TCP-based services. These services are contained in legacy systems, or travel across enterprise message buses via APIs and protocols such as TIBCO EMS, JMS, RMDS, AMQP, XMPP, and Stomp.

Some applications may be composed of several subsystems, each using a different application protocol. For example, one subsystem may require a publish/subscribe programming model that listens and responds to the changing prices of inventory items, another subsystem may receive a large volume of database events pushed from a column-based persistence engine, and yet another subsystem may need to support chat and chat rooms.

By using WebSockets, your application can avoid siloed solutions for each subsystem. You no longer have to use hacks to push data to a browser or use CPU and network-intensive polling to simulate publishing and subscribing. With WebSocket, the W3C and IETF standards bodies have provided an elegant way to enable full-duplex network communication over the Web. In addition, since WebSocket traffic flows over standard HTTP ports (80 and 443), there is no need to open additional ports on corporate firewalls to take advantage of full-duplex communication.

4. Your application developers need an API that is easy to use.
To deliver a compelling, usable application, developers rely on rich client platforms such as Adobe Flex (Flash), Microsoft Silverlight, Java/JavaFx, and JavaScript. However, connecting these rich clients to real-time data over the Web can be challenging. Developers often have to create their own client- and server- side communication libraries, essentially reinventing the wheel to overcome some of the inherent limitations of HTTP.

Consider how much time and effort is required to create a reliable two-way communications protocol and to connect an application server to back-end systems. Testing and securing applications built on top of this protocol is difficult, because it is harder to pinpoint the problem in a proprietary protocol. Moreover, the work is application-specific, thwarting all attempts to re-use it.

HTML5 WebSockets offer a single, standard interface against which to develop. This means developers can spend less time building and testing communication protocols and more time designing a superb client-side experience - without having to redo the back-end work. HTML5 WebSockets eliminate much of the custom development work that engineers have to do to create a fast, secure, full-duplex application.

5. Your application must extend SOA over the web and in the cloud.
Your enterprise service-oriented architecture (SOA) application or SOA product works well on an internal enterprise network, but you now have to deploy your high-performance distributed software over the web - and through the quagmire of firewalls and proxy servers along the way - to leverage all the advantages of a web infrastructure for your demanding customers and even more-demanding management.

With WebSockets, your applications can open a standardized, full-duplex connection over the web. Developers can leverage this connection to extend messages from a SOA inside the firewall to an external SOA, such as a high-performance Enterprise Service Bus (ESB) or a web-based Supply Chain in a cloud environment.

HTML5 WebSockets are more efficient than current architectures, and WebSocket applications can handle more concurrent users and a greater message volume, with less infrastructure. This ability is good for any application that has to deal with capacity constraints, as the number of servers required is lower. Where this really makes a difference, however, is in on-demand computing environments in public and private clouds. In a cloud-computing model, capacity is elastic: you pay for what you use.

Traditionally, there are two ways of handling growing demand. The first is to scale "vertically," which involves buying a bigger machine, adding RAM, and so on. Modern web applications do not use this approach; however; they scale "horizontally" - that is, to handle an increasing load, you add more machines at each of the tiers in the application.

Web applications deployed on elastic computing platforms must be especially aware of their resource consumption. In a cloud, the addition of machines is often automated, so there is no upper limit on resource consumption. Now, inefficient code translates directly into a higher bill at the end of the month, because more virtual machines were spun up to handle the traffic. In these environments, the efficiency of HTML5 WebSockets is particularly compelling.

Summary
This article showed you five reasons why you should be using WebSockets for your web applications. You learned that HTML5 WebSockets can enable true full-duplex communication, can handle large numbers of concurrent users, can extend TCP-based protocols to the browser, is easy to use, and can extend your SOA over the Web and in the cloud.

• HTML5: Media in a Flash...Without Flash!
• How to Deliver Rich Web Apps Accessible from Any Web-Enabled Device
• Kaazing Launches Its Platform in the Amazon Cloud
• Akamai’s Chief Product Architect on SPDY, WebSocket, and Kaazing