Monthly Archives: April 2014

Trying WebSockets with Gorilla and Knockout

Shared Form Demo

I have been wanting to try out a few technologies for a while and tried them all out in a demo that allows concurrent distributed users to edit the same web form.  All the users see edits happening in real time.  The code is on github, and the README there has more detail than I supply here. The demo works, but the README mentions things that a real-world shared form would need added or at least considered.

https://github.com/ecashin/go-getting/tree/master/web/shareform

These are the technologies I used:

I also touched on a couple other primitives that would be needed to go beyond the demo stage:

I also used good old jQuery.

The amazing thing about this experience was that all these technologies worked wonderfully, without a hitch.  They were pretty easy to put together.  One reason is that each has great documentation, although the Gorilla WebSocket module’s best documentation is external to it, in a blog post by its author, Gary Burd:

http://gary.burd.info/go-websocket-chat

While driving, I listened to a bunch of conference talks and tutorials on WebSockets.  I found out that about half of the presentations dwell on fall-back strategies, ways of supporting users with lame browsers or lame web proxies.  It turns out that there are a few libraries created expressly to provide transparent fall-back mechanisms when the client can’t use WebSockets.

Both have a two-part implementation: There is a client-side JavaScript library and a server-side part.

There isn’t any Golang server-side Socket.IO or Sock JS implementation that is “blessed” by either of the two projects or even stable at this time.  It leaves me wondering whether I could put Sock JS in the client and just provide support for long-polling AJAX in the Golang server as the sole fall-back mechanism.

Knockout JS was the most fun part of this experiment.  It does dynamically tracked dependencies between data in the running JavaScript and data in the DOM, allowing two-way binding between the DOM and the “ViewModel” in the JavaScript runtime.  You can manipulate the ViewModel based on messages coming through the WebSocket, and the data in the DOM gets automatically updated.  It is loads of fun to see in action.  The Knockout JS site has interactive tutorials where you can try it:

http://learn.knockoutjs.com/#/?tutorial=intro

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