Question

I would like to find a good (up-to-date) Java Trail type beginning tutorial on Websockets, with both Javascript client code and Java server code (that actually works). On the server side, if all I have to do is create a simple socket server or something like that, please tell. I have so far found nothing (although I’ve googled for hours) that provides the essential basic information like this (except on the client side, which is apparently very easy).

I’m not interested in using existing Websocket server systems (other than starting with a simple copy-paste from a simple tutorial). If you’re interested, I’ll tell you why below.

I have an open-source project that’s been begging for HTML5 since long before it began (from its initial conception many years ago). Getting the two-way communication from Websockets as opposed to long-polling, forever-frames etc. looks like a winner to me. The current version of the (framework) software is HLL “light” – with my typical emphasis on not dragging in extra code. It uses Java SE only, although I intend to build version(s) using EE communications. I can at present easily install the whole framework with room to spare for application components on small devices like cell phones.

1. I want minimum code.
2. I pride myself on understanding all the code in the system.
3. I think it’s death to a new open-source project if you have to tell people who want to try it that they have to download and install all sorts of other open-source code to do it.
4. I don’t want my code subject to changes in somebody else’s code.
5. This really shouldn’t be all that difficult – if I just find the right documentation.

UPDATE: I no longer need a simple tutorial on websockets. I’m well on my way to having built a production class websocket server and have a very nice browser-based client to use for testing. I am now building a non-browser-based client to go with it. Building a multi-client websocket server that implements the full standard isn’t simple, btw. (In hindsight – it’s no wonder I didn’t get any answers.) And if it’s going to work as a stand-alone server for browser-based clients, it needs http (to provide the web pages at least) and other stuff. Not a project for the faint of heart or someone with little time to put into it.

Answer 1

Since first posting, I’ve been building my own WebSocket server. Dreams that all this would be simple quickly passed. I am however, getting close enough to mention the word “release” as in free Beta for anyone who wants a websocket server. (Notice I’m just “mentioning” the word – I’m still at least a couple of weeks away.) It’s a multi-user server that’s light-weight and screamingly fast. I’ll eventually add http support so no other server will be needed for delivery of web pages (WebSockets are upgraded http connections anyway). I’ll also be adding HLL functionality. First thing about that is that it will simplify application. Even though I’ve worked consistently to maintain “light-weight” status, this whole combination has been a life’s ambition and I believe developers will find it amazing for building anything from simple and direct to large scale complex, distributed, intelligent systems.

I’ve used the most recent version of the standard, which is the final draft version, and will probably be very close if not the same as the final standard; version 1. So far, it works with Chromium (Chrome dev) and Firefox. There is however, apparently some code in their WebKit that provides support for other browsers. I haven’t tried that yet. With the browser, I’ve so far made the connection and pass text messages (large and small) back and forth. That’s all I’ve discovered so far that the browser handles. I take it support for very large text “messages” would really only be used for file transfer in conjunction with HTML5 local storage capabilities. I haven’t tried that yet either. Binary transfers will likely be connected to HTML5 streaming video and audio at some point, but I haven’t run across any mention of it so far.

I’m currently working on a Java client that will support the full standard, including pings and binary transfers, file transfers – the whole ball of wax. Most of what I need has already been built for the server and its “echo” application which includes message sending just like a client. I will then revisit some of my earliest work to generalize in a nice way when adding the new functionality. Having one or more Java websocket clients in applications will be a good thing in many cases, I think. And it’ll give the the full capabilities for web browsers as well, whenever they’re ready for it.

I also know that Opera is quite popular among HTML5 enthusiasts. I actually started using the version of the standard that they support so it shouldn’t be difficult to add it. (Just fooling around trying to find my way – and got the stuff specific to that version working.) I’m seriously tempted to spend the time putting the support in for that version even though it should become totally obsolete within a few months. It’s just that Opera is very good on the other HTML5 stuff and there’s a large crowd of enthusiasts using it. On the other hand, they mostly work on the browser-client side, and I don’t know if they’ll get involved much on building server-side applications.