WebSockets noob working with Railo

Question

I am admittedly a complete noob in all things server, Linux, and websockets. I finally managed to set up a VM running Apache, Tomcat, and Railo that I could connect to and serve up CFM pages, all the while learning UNIX command line navigation, server theory, etc, etc...

Here's my problem -- there is only one Railo websocket extension and it is super rinky-dink (I had to modify the CFC just to get the service to start) but I can't get a websocket connection up (I keep getting "unexpected code 200" in Google Chrome). There is minimal documentation, which is not helpful at all.

Basically, I am trying to do some prototyping for a future project that will use websockets. I like Railo for its speed, security, and excellent ability for very database heavy operations. I am interested in Node, but don't know how to get the same security and DB functionality out of Javascript as I can with CFML.

So I have a couple questions: what are my best options for WebSocket servers? Should I be trying to use Apache and/or Tomcat? People keep saying it's totally not worthwhile to have something like Node.js running the websockets portion and something else doing the heavy lifting behind it -- why is this? I'm more than happy writing WS handlers in whatever language if I can just get a nudge in the right direction, some excellent tutorials (I can't seem to find much in this department), or good feedback on how to, from the ground up, set up my Linux box to handle websockets -- and preferably how to handle both websockets and a robust language like Railo.

Answer 1

The Railo extension works fine for me. What about submitting some test code so that we can debug it? Of course the websockets projects is very young and in full deployment. So feel free to fork and submit patches or suggestions. You have plenty of options:

• Railo Google Group https://groups.google.com/forum/?fromgroups#!forum/railo

• Github Extension Repository

• submit a but in the Railo Jira bugtracker

Answer 2

The "unexpected code 200" is caused by Railo's web socket server sending an outdated response. They changed the web socket spec and Chrome uses the newer spec.

The problem seems to be caused by chrome & co implementing the new spec, "draft-ietf-hybi-thewebsocketprotocol-17". It requires the server to respond with "HTTP/1.1 101 Switching Protocols" rather than 200 OK.

The solution here would be to either update the Railo web socket extension yourself or use some other solution:

Here is a complete demo of a web socket chat server written in PHP.

http://www.flynsarmy.com/2012/02/php-websocket-chat-application-2-0/

I have used this myself to implement a real-time HTML chat served from an Arch Linux machine that I had lying around. Configuration consisted of simply setting up Apache and PHP then changing the IP address in index.html and in server.php to the external ip address of the server machine.

This flynsarmy demo includes a recent version of PHPWebSocket which is an open source web socket server written entirely in PHP and contained in a single file. The demo hooks into three callbacks: connect, message recieved, and disconnect.

The important thing to note, for me, was that the web socket protocol supports text only, not binary so while extending it for my own chat app I had to implement my own commands to help control the server. Commands in my case looked like this:

!kickusers: username, another_username, a_third_username

My server code would check the first character of all messages for a '!' and if present would treat it as a command. Then I slice up the string to get the command "kickusers" and a list of users to kick. Then I call the appropriate kick function and pass it the array of usernames.

Since my scenario was a chat client this meant that the user could literally type this command into chat and the server would accept and respond to it.

The way all this is deployed on my server is like so:

• I have Apache serve the index.html page when the user goes to that location on my server in their browser. The only purpose Apache plays here is to give index.html to the client who requested it.
• The index.html page contains html to display the chat and javascript to send and recieve chat to/from the server. Basically, index.html is simply a chat client written in HTML and Javascript and it runs in the browser.
• I run server.php via ssh on the server to start up the WEB SOCKET server (totally separate from Apache) which just sits there and handles chat stuff like echoing text to the other connected clients etc.

Though the Arch wiki on installing Apache and PHP is specific to Arch in the way that you install the Apache and PHP packages the sections on configuring Apache and PHP apply to all. I'll save you the google query and give you the link here if you like: https://wiki.archlinux.org/index.php/LAMP

As for prototyping, the reason I gave the link to Flynsarmy's chat demo is because his comments are helpful, he wrote a blog about it, and it comes as a very simple yet complete example of how to do something with web sockets in php.

Answer 3

The main problem of node.js is that it's mono-thread : you won't be able to do background tasks using it and local IO will block your server.

A solution I use is Go. It's very fast, has very good concurrency features and has integrated websocket and json libraries (sample : http://gary.beagledreams.com/page/go-websocket-chat.html). An efficient web application server is made in a few dozens lines of Go. You'll find that there is still much less documentation on internet than for java or even node.js through.

There are a few implementations of websockets in java but as I'm in the process of switching everything I had in java to Go I hadn't tested them. I know I use Google gson for the json encoding in java and it's very good.