I am building a java chatting web application.(Server and Client in one project)
follow is my condition
Springframework 4.2.3
JSP
Maven Project which converted from a Dynamic Web Project
Unable to use node.js
So User scenario in my head is
User enters some text and press Send
Ajax call to deliver messages to server
Server checks the users who are currently connected(from Session maybe)
Server calls other users script to append new message
I am quite confusing with step4. Is it possible that Java calls DOM event trigger?
How could a client get a new message event from server?
Thanks. :D
P.S.
These days majority of chatting servers are event-driven. Is it possible to build an event driven chatting server with Java?
Your solution is formed as if there is no WebSocket technology available to you. WebSocket is implemented to solve real time messaging issues. It pushes message to the destination.
But if to stick wih your method following is meaningful.
You need someplace to keep incoming messages such as database or session.setAttribute [bad idea]. Then use some ajax call loop on the clients machine to ask for a new incoming message from server.
Probably your server will slow down due to incoming flood of GET requests from multiple users.
to Your last question in post scriptum: yes, I use tomcat websocket api.jar in my projects. There is well written documentation on apache.org
As I mentioned, learn WebSocket if your users are not using old internet explorer browsers. There are bunch of tutorials on it...
I am working on attendance system where project management system is also handling using Javascript\Jquery at client side and PHP\MySQL at server side.
A feature in my web app is user message to admin. For this I have applied an ajax request which is made by setTimeout function (after every 15 seconds) to check that is there any new message comes in database if yes then return it to the admin.
It working fine but the drawback is (as you know) continuous request to server which really poor and bad. As I know that real time functionality can solve this problem I have checked some link websocket.io and signlR but there are applicable with Nodejs and asp.net.
So, how can I apply real time functionality with php or I get that new data have reached in to database without continues request with ajax.
There are actually some PHP tools for doing this now. For instance, check out Ratchet.
It's also possible to do bi-directional sockets by creating a simple TCP/IP server. I've done this before for bi-directional communication between a PHP server and a desktop app.
http://php.net/manual/en/sockets.examples.php
Of course I am aware of Ajax, but the problem with Ajax is that the browser should poll the server frequently to find whether there is new data. This increases server load.
Is there any better method (even using Ajax) other than polling the server frequently?
Yes, what you're looking for is COMET http://en.wikipedia.org/wiki/Comet_(programming). Other good Google terms to search for are AJAX-push and reverse-ajax.
Yes, it's called Reverse Ajax or Comet. Comet is basically an umbrella term for different ways of opening long-lived HTTP requests in order to push data in real-time to a web browser. I'd recommend StreamHub Push Server, they have some cool demos and it's much easier to get started with than any of the other servers. Check out the Getting Started with Comet and StreamHub Tutorial for a quick intro. You can use the Community Edition which is available to download for free but is limited to 20 concurrent users. The commercial version is well worth it for the support alone plus you get SSL and Desktop .NET & Java client adapters. Help is available via the Google Group, there's a good bunch of tutorials on the net and there's a GWT Comet adapter too.
Nowadays you should use WebSockets.
This is 2011 standard that allows to initiate connections with HTTP and then upgrade them to two-directional client-server message-based communication.
You can easily initiate the connection from javascript:
var ws = new WebSocket("ws://your.domain.com/somePathIfYouNeed?args=any");
ws.onmessage = function (evt)
{
var message = evt.data;
//decode message (with JSON or something) and do the needed
};
The sever-side handling depend on your tenchnology stack.
Look into Comet (a spoof on the fact that Ajax is a cleaning agent and so is Comet) which is basically "reverse Ajax." Be aware that this requires a long-lived server connection for each user to receive notifications so be aware of the performance implications when writing your app.
http://en.wikipedia.org/wiki/Comet_(programming)
Comet is definitely what you want. Depending on your language/framework requirements, there are different server libraries available. For example, WebSync is an IIS-integrated comet server for ASP.NET/C#/IIS developers, and there are a bunch of other standalone servers as well if you need tighter integration with other languages.
I would strongly suggest to invest some time on Comet, but I dont know an actual implementation or library you could use.
For an sort of "callcenter control panel" of a web app that involved updating agent and call-queue status for a live Callcenter we developed an in-house solution that works, but is far away from a library you could use.
What we did was to implement a small service on the server that talks to the phone-system, waits for new events and maintains a photograph of the situation. This service provides a small webserver.
Our web-clients connects over HTTP to this webserver and ask for the last photo (coded in XML), displays it and then goes again, asking for the new photo. The webserver at this point can:
Return the new photo, if there is one
Block the client for some seconds (30 in our setup) waiting for some event to ocurr and change the photograph. If no event was generated at that point, it returns the same photo, only to allow the connection to stay alive and not timeout the client.
This way, when clients polls, it get a response in 0 to 30 seconds max. If a new event was already generated it gets it immediately), otherwise it blocks until new event is generated.
It's basically polling, but it somewhat smart polling to not overheat the webserver. If Comet is not your answer, I'm sure this could be implemented using the same idea but using more extensively AJAX or coding in JSON for better results. This was designed pre-AJAX era, so there are lots of room for improvement.
If someone can provide a actual lightweight implementation of this, great!
An interesting alternative to Comet is to use sockets in Flash.
Yet another, standard, way is SSE (Server-Sent Events, also known as EventSource, after the JavaScript object).
Comet was actually coined by Alex Russell from Dojo Toolkit ( http://www.dojotoolkit.org ). Here is a link to more infomration http://cometdproject.dojotoolkit.org/
There are other methods. Not sure if they are "better" in your situation. You could have a Java applet that connects to the server on page load and waits for stuff to be sent by the server. It would be a quite a bit slower on start-up, but would allow the browser to receive data from the server on an infrequent basis, without polling.
You can use a Flash/Flex application on the client with BlazeDS or LiveCycle on the server side. Data can be pushed to the client using an RTMP connection. Be aware that RTMP uses a non standard port. But you can easily fall back to polling if the port is blocked.
It's possible to achive what you're aiming at through the use of persistent http connections.
Check out the Comet article over at wikipedia, that's a good place to start.
You're not providing much info but if you're looking at building some kind of event-driven site (a'la digg spy) or something along the lines of that you'll probably be looking at implementing a hidden IFRAME that connects to a url where the connection never closes and then you'll push script-tags from the server to the client in order to perform the updates.
Might be worth checking out Meteor Server which is a web server designed for COMET. Nice demo and it also is used by twitterfall.
Once a connection is opened to the server it can be kept open and the server can Push content a long while ago I did with using multipart/x-mixed-replace but this didn't work in IE.
I think you can do clever stuff with polling that makes it work more like push by not sending content unchanged headers but leaving the connection open but I've never done this.
You could try out our Comet Component - though it's extremely experimental...!
please check this library https://github.com/SignalR/SignalR to know how to push data to clients dynamically as it becomes available
You can also look into Java Pushlets if you are using jsp pages.
Might want to look at ReverseHTTP also.
Using a browser, is it possible using client only technologies (like JS, HTML ...) to send data to another browser without going through the server that servers the HTML page?? I mean if both ends are already synchronized (one has open a port, and the other one sends the data), is it possible to do that?
With only javascript and HTML, the answer is clearly no : you can't establish a direct P2P connection.
There are solutions involving a plugin, for example java (in the case of java, the user has to relax security, usually through signing).
But note that with websockets you connect and exchange through a server but it's efficient enough for most uses (provided your users will accept not to use IE9-). WebSocket programming is easy enough those days (here's an example of a complete chat client/server, googling would give an example for your favorite language) so I really recommend not to try using a plugin.
HTTP requires a server. For personal projects you can try the web server plug-in for Firefox:
https://addons.mozilla.org/en-us/firefox/addon/pow-plain-old-webserver/
You can't do a direct client-to-client transaction with JS, HTML yet, but if you check red5 to uses Java frame work, it provides RTMP(Real Time Media Protocol) which for P2P connection.
Introduction: I want to develop the chat client that user can chat on the browser and I use the protocol call xmpp. Because of HTML5 web socket not yet available I try flash xmlsocket instead.
Problem: I cannot connect to the server via browser. I'm not sure why, but I think that it is the problem of the server configuration.
Question: Which is the best jabber server suitable for this job?
Most probably this is a permission issue. Either that or you've just configured the wrong host/port to connect to. Flash is not allowed to connect to other hosts than the one it was gotten from itself. You have to explicitely allow flash connections on the receiving side of the request (so on the chat server that you are connecting to). Google for crossdomain.xml to get more info.
ejabberd sounds like a suitable option for you. ejabberd is xmpp server written in erlang and is used quite widely. Many of the well known web based im services like www.meebo.com etc are known to be running on ejabberd. It allows you to install other transports which would let you enable talking to users of other protocol like yahoo, msn, icq etc.
You can also have a look at the xiff action script library by ignite realtime. It is an xmpp client library in action script. If you use this library you would just need to implement the ui components.
Hum... flash is ok, but you'd be better of using something like BOSH, which is basically an HTTP layer over XMPP.
Ejabberd would be a good server, as it supports BOSH, I don't know about OpenFire or Tigase (but I'd say they do). Other servers should be looked at carefully because they don't seem to have a "dynamic" community.
You will need a lot of Javascript, and for that, I can recommend StropheJS, which is probably the very best library out there today.
We have created a MUC (Multi-user chat room) client called Aristochat that works in the browser recently at Superfeedr. You can find the code on Github and an example here.