Implementing COMET clientside - javascript

I have read up about what COMET streaming is, and all the various hacks required to get it working across the major browsers. The problems encountered seem to be two fold: 1. Server being able to support many persistent connections 2. Implementing the JS functionality
I have an application where I need to perform COMET streaming. I have already tackled the first problem above - I have a custom server running which delivers updates as it arrives in chunks. I want to now be able to connect using JS to this URL, so I can receive the updates.
Is there a simple COMET library I can use for this? I saw the Orbited project. Can I use the client side JS of orbited to perform this? What kind of modifications do I need to perform in the backend for this?

If you can get your server code to conform to the Bayeux specification then you can use any of the existing cometd javascript implementations, current available in DOJO and jQuery. Unfortunately, the spec is quite complex, especially if you want to do both long-polling and callback-polling. You may be better of just running an existing cometd server like Jetty and then writing a client library for your server code to push data to it.

Related

jQuery alternatives for multiplayer games?

First off, I am not asking for any code or anything like that.
all I need is some advise.
I'm creating a roulette game and everything in my roulette game is based on jQuery.
however, as we all know, jQuery is client side so I was thinking about using AJAX to send some details back to server and from the server to the users browser so I can make this roulette game work in "multiplayer" fashion... But the issue is that I don't think its possible to send the roulette's wheel animation to the server and back to users browser so I am a bit confused about this!
In my research I came across some information (old ones) about using node.js and jquery together! I don't know if this is possible or how easy it would be to use my jquery code in node.js as I have never used node.js before..
so the question that i have is:
based on the information i provided above and my requirements, what are my options?
can I use AJAX to achieve what i am trying to do and if so, a bit
information would be great.
if AJAX is out of question, is it possible to use my jquery code in
node.js to achieve what I am trying to do?
ANY ADVISE WOULD BE APPRECIATED.
P.S. I don't want to use HTML5 as 1st I don't know much about HTML5 and also, some devices, browsers do not support it.
Thanks
The best way is to use websockets to ensure real time communication. One of the best alternatives for implementing that could be using a server under node.js. Have a look to this video from Code School node.js tutorials: https://www.youtube.com/watch?v=mtDK4jf4RS0 where is ilustrated how to implement a real time chat. Your problem is based on the same.
There are three parts to a multiplayer game displayed in a browser:
client-side display,
server-side data management,
client-server communication.
If you're already set on your display technology (jQuery), then you're probably going to use $.ajax() for client-server communication. However, technologies used for server-side data management are completely up to you and they don't necessarily have any connection to the technologies used for display and communication (meaning the traditional communication initiated by client).
Basically, use any kind of server technology stack you like. Node.js might do just fine but there are many other viable alternatives. They just need to support communication with the client.
So, to be absolutely clear, your question doesn't really make sense. You might use jQuery in the client and Node.js on the server, but they will never really "work together". They will manage completely separate parts of your application and connect through protocols not specific to either of them.
As for the animation, the animation itself is solely a client-side problem. If you want to "synchronize the animation" across multiple clients, you can let the clients communicate with the server, but they only ever need to send/receive plain data. Then you adjust the client-side animation based on the received data.
As another poster points out, websockets are a better fit for this than regular client-initiated HTTP requests. Not because of "the animation", but because you want all the clients to receive the information about the start of betting at the same time.
I am also developing a MMO game using javascript only. Firstly, there are two different types of javascript here. Usual client side javascript (the one you already know) and the server side javascript (i.e. Node.js).
You will need to develop both client and server before connecting them with jQuery's Ajax. So you need to study Node.js before designing overall architecture of your game.
I read many Node.js tutorials and watched many youtube tutorial videos but I was still confused, before I really sat down and read a good textbook that explained from basics, one like below. Try to get hold of it from your local library.
Express web application development learn how to develop web applications with the Express framework from scratch by Hage Yaapa
Express is the popular framework that runs on Node.js now. So it's worth getting familiar with Express Framework. Once you understand how express app works (not so difficult), you will see how you can frame your game structure like I did :)
In order for many clients to share same animation, there must a server that synchronizes the game state. Ajax can only link between server-client communication in my understanding. There is no mechanism that connects between clients. The clients ask server what number was the result of roulette roll and show the corresponding animations.
Yes, you can use NodeJS and jQuery together.
NodeJS is server-side, meaning that you set up a server (a lot of people use the Express module, which is easy to use), which serves content to clients asking for it. Your server-side code can be in any language supporting sockets, not just NodeJS. But NodeJS is easy to use if you know JS already.
jQuery is client-side, meaning that it's executed by the user's browser, and may or may not have a server-side component (if it doesn't need it), or it might have one where it sends requests to the server-side code. When it requests a page from the server, it can be static content (like when you request index.html) or dynamic via an AJAX request. Client-side browser code must be HTML/CSS/JS (you can't make Firefox or Chrome interpret C, for example).

Understanding Node.js use cases

Trying to understand using node.js for a web applications.
Are there basically 2 major uses cases, i.e.:
The entire system is written in node, so you have functions for login, logout, password recover, and whatever else the web app does. All of this is written in javascript?
You use node.js only for sending the client updates, to have a real-time effect on the app. But the rest of the application is written in e.g. rails or django
Please tell me if I understand this correctly:
In terms of other technologies used with node.js, you tend to see people using node.js as the backend server, socket.io on the client side to establish a cross-browser long running ajax call library, and then you might use backbone.js for your client mvc pattern.
Is this right?
Basically speaking, it is just a tool to run javascript code server side. What you do with it is up to you. Many are using it as a complementary system since it's relatively new, but it's perfectly possible to run an standalone app with node.js.
It's said to be particularly good at handling concurrent connections, which is why it is often recommended to handle real-time jobs within an app, but there is no "obligation" so to speak to use it for this specific use case, it's just one thing you can do.
As with everything, the best way to understand it is to use it, so don't be afraid to play around with it.
Use case for Node js as we are using in our Application
Skype like voice & video chat on chrome browser using node js

GWT server with get() and post() built on client end

This is more of a curiosity really, to see if some one has done anything similar, or if at all it is possible.
I'm working on a project that will get notification through external notifications. Now I could go about doing this by having notifications coming to my server and have a comet setup between my client and server.
BUT
I was wondering if I could write server logic into my client and listen out for notifications from external sources. Immediately one issue I see is, external sources would need callback URL etc, which I dont know if you could do from client side (unless one could use the IP address in that way).
As you can see it is more ideas and discussions if such a thing was possible, this is somewhat inspired by P2P models whereby you wouldn't be mediating things through your central server.
Thanks in advance!
GWT compiles (nearly) Java source into JavaScript, so compiled GWT apps can't do anything that traditional JavaScript running in the browser cannot do. The major advantage of bringing Java into the picture isn't automatic access to any/all JVM classes, but the ability to not only maintain Java sources, which tend to be easier to refactor and test as well as keep consistent with the server, and to compile that statically defined code into JavaScript, performing all kinds of optimizations at compile time that aren't possible for normal JavaScript.
So no, while you can have some code shared by the client (in a browser) and the server (running in a JVM), you can't run Tomcat/Jetty/etc in the browser just by using GWT to compile the java code into JS.
As you point out, even if this was possible, it would be difficult to get different clients to talk back and forth, without also requiring that the browsers can see and connect at will to one another. BitTorrent and Skype have different ways for facilitating this, and currently browsers do not allow anything like this - they are designed to make connections to other servers, not to allow connections to be made to them.
Push notifications from the web server to the browser are probably the best way forward, either through wrapping comet or the like, or through an existing GWT library like Atmosphere (see https://github.com/Atmosphere/atmosphere/tree/master/samples/gwt-demo for a demo).

Adding WebSockets support to local web server

I'm developing a multiplayer Javascript/canvas game that uses WebSockets to communicate player positions and states etc. I'm comfortable coding this in Javascript, but it's the server-side websockets stuff that I'm having trouble with.
I have no idea how I should implement WebSocket support past the client side Javascript. Do I add a module to Apache? Do I do it in PHP? Do I use something like node.js? As far as I know node.js has received a lot of praise about this sort of stuff, but I still have no idea what it really is other than a web server.
I would recommend using nodejs, along with socket.io, which is a cross-browser compatible web sockets style library. It makes it really simple to write code which communicates with the server (==nodejs) in real time. It uses web sockets in browsers which support them, or other technologies in browsers which don't.
Just a note regarding PHP since you mentioned it... It is not very suitable for this in my opinion, since, as you may know, a PHP script only lives the duration of the request. This behavior makes it difficult to implement real time communication, unless you roll your own server with PHP, skipping Apache or such entirely.
Another alternative could be using Python, and perhaps something like Twisted, although you may need to implement websockets or such yourself.

Handle Web Server with multiple clients [duplicate]

I am looking for a simple and reliable Comet javascript library. I want to keep a persistent streaming of data from my server (via PHP script) to the client side. I tried building my own using the iframe technique, but there are lots of issues with safari which I experienced. I am just hoping someone else has created a simple library for it?
There is a jquery comet plugin
Probably the best version though is the Dojo library
I have a quick list of commands I used to get a jetty server with comet up and running here
It's not just the javascript library that you need, but a server-side implementation as well. Depending on your needs, you'll need to pick a proper implementation.
You mentioned PHP, which is typically difficult with long-held requests. Other options include having a separate server for your comet requests, or using a SaaS solution, such as WebSync OnDemand.
Depending on which option you pick for the server, you will have one or more javascript clients available. But you need to determine your server implementation first, then use the appropriate javascript implementation to match.
Have a look at http://www.ape-project.org/ Pretty quick setup process.
have you tried JSON-RPC. Apparently Dojo has good support for it, though I haven't tried it thoroughly
JSON-RPC
Dojo Documentation

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