Real-Time Messaging

Reuven Lerner — Thu, 14 Mar 2013 16:45:05 +0000

Want to send messages to all the browsers connected to your site? The pub-sub paradigm, run through Web sockets, might be just the solution.

Back in the 1980s, BSD UNIX introduced the idea of a "socket", a data structure that functioned similarly to a file handle, in that you could read from it or write to it. But, whereas a file handle allows a program to work with a file, a socket is connected to another process—perhaps on the same computer, but quite possibly running on another one, somewhere else on the Internet. Sockets brought about a communications revolution, in no small part because they made it easy to write programs that communicated across the network.

Today, we take that for granted. Dozens or hundreds of sockets are open on my computer at any given moment, and I don't know if they're communicating with local or remote programs. But, that's just the point—it's so easy to work with sockets, we no longer think of networked programs as anything special or unusual. The people who created sockets couldn't possibly have imagined the wide variety of protocols, applications and businesses that were built using their invention.

My point is not to praise sockets, but to point out that the inventors of a technology, particularly one that provides infrastructural support and a new abstraction layer, cannot know in advance how it'll be used.

In that light, consider a new network communication protocol called Web sockets, part of the standards known collectively as HTML5. To me, at least, Web sockets are the most undersold, least discussed parts of the HTML5 suite, with the potential to transform Web browsers into a fully fledged application platform.

Web sockets don't replace HTTP. Rather, much like BSD sockets, they provide bidirectional, long-term communication between two computers. The "bidirectional" and "long-term" aspects distinguish Web sockets from HTTP, in which the client sends a request, the server sends a response, and then the connection is terminated. Setting up a Web socket has very little overhead—and once communication is established, it can continue indefinitely.

Now that Web sockets exist, and are even supported by a growing number of browsers, what can you do with them? That question is still hard to answer, in no small part because Web sockets are so new. After all, if you had asked someone in the 1980s what you could do with BSD sockets, it's unlikely that streaming video would have come to mind.

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Web Sockets

Real-Time Messaging