Hello people and bots,
I'm developing the front-end web application for a system and have hit a little problem.
The whole application has to be on one page, meaning no refreshes or page changes during the flow of the major areas of the application.
It also has to work in all web browsers including IE7 and be deploy-able as a HTML5 application for tablets and mobile phones.
It's based around a user logging in, which is regulated by webforms authentication, then I need to poll or long-poll the server for updates. This would be simple if I could do a request for each part of the system, however if the system gets too big session blocking becomes a problem and it could also end up ddosing itself. So what I need to do is think of a way to send one request and build one response from that request.
My first idea was to build a response model with JSON or XML and let JavaScript regulate what needs to be updated. For example, a new comment has been made on a topic, all the clients see this update near instantly. My idea was to send something like this:
[
'd':
{
'addComment' : [{'topicId':'topic1', 'description':'haha'}, {'topicId':'topic1', 'description':'lol'}],
'addTopics' : ['topic2','topic708'],
}
]
JavaScript would then parse this and add "haha", and "lol" to the element with the id "topic1". In theory it seems quite simple to achieve, but as the system is getting bigger it seems to constantly be turning into a big mess.
My second idea was to simply have a set of client-side functions for adding and removing stuff in the DOM, And then use a JSONP technique to call this function.
var addComment = function(commentModel)
{
var topic = document.getElementById(commentModel.topicId),
comments = topic.getElementByClassName('comments')[0],
comment = document.createElement('div');
comment.innerHTML = commentModel.description;
comments.appendChild(comment);
updateUnreadComments();
}
Response:
(function(addComment){
addComment({ topicId : 'topic1', description : 'haha' })
addComment({ topicId : 'topic1', description : 'lol' })
})(addComment)
Personally I find both methods a rather annoying workaround for nothing more than simple broadcasting.
I was wondering if anyone else has ever had the same problems and if they have ever come up with a more creative solution.
I would also like to know what kind of security issues I could expect with JSONP.
All help is appreciated!
You may take a look at SignalR. Scott Hanselman also blogged about it.
Related
I want to use a linux device like a BananaPi with a socketcan-compatible can-controller to connect to a automotive can-bus and show its data in realtime on a webpage, which should be hosted on the Pi.
The data should be listed as hex-values and visualized via graphs (the different signals, for example the current speed).
After some research I discovered node-can and I could get managed to show the can-messages as a list on a webpage. But I noticed, that the messages come with a quite huge delay (~2 secs) when there is a huge busload (I sent can messages in a 1 ms period). The same delay occurs, if I use the following minimalistic example:
var can = require('socketcan');
var channel = can.createRawChannel("can1", true);
channel.addListener("onMessage", function(msg) { console.log(msg); } );
channel.start();
I am absolutely new in this topic but I think, that nodejs isn't the best choice to realize this project?
Are there any other (better) methods to realize such a system?
I could imagine something like a C-backend, for example based on candump (with this program no delay occurs at the same busload), and a frontend realized with javascript, html and css. But I have no idea how to get those different single programs together. Could you give me a keyword so I have a starting point for further research (websocket?!)?
I also thought about writing the can frames in a sql database and grab them from the database for the webpage-gui but I have no idea, if/how this works and if this is fast enough....
Thanks in advance!
I'm building an android application that uses Parse's push functionality to send messages between single users, and after a lot of finagling around with different solutions (without enabling Client Push because that's apparently a security risk) I settled on this:
// com.myapp.Application.java
public void onCreate(){
...
ParseInstallation i = ParseInstallation.getCurrentInstallation();
i.put("username", ParseUser.getCurrentUser().getUsername());
i.saveInBackground();
...
}
Now, when I want to send a push to a single user, I call a Cloud Code function that does this:
// cloud/main.js
Parse.Cloud.define("pushMessage", function(request,response) {
var from = request.user.getUsername();
var to = request.params["receiver"];
var query = new Parse.Query(Parse.Installation);
query.equalTo('username', to);
Parse.Push.send({
where: query,
data: {
alert: "message from " + from,
// more data
}
}
}
This feels a bit like a hack, but it works. Is it bad form? I can't really wrap my head around the solutions I've seen so far, mostly because they're almost exclusively geared toward iOS and I can't read objective-C.
Okay, so I had to re-do this. I'll answer it just in case someone has the same problems.
The issue with including the username in the installation is that you need to make sure that you handle it correctly. The installation is, as the name implies, tied to the device instead of the user. This means that if your application supports several users, it's one extra step to handle on relog, otherwise users will get pushes not meant for them.
I forgot about doing some of that, and my code turned into sphagetti.
After digging around for a bit, I changed the method to instead subscribe to a channel named after the user's ObjectId, and simply sending pushes to that channel. I then unsubscribe on logout and resubscribe every time the application opens. That way, if you close the application you can still receive pushes. It works just as well, and requires less code.
I will do my best to explain my problem to avoid people pointing me into different directions.
I got an assignment from business people. I don't know the terminology. It is very similar to email notification, message notification on facebook, notification on social media games.
For example, people are sending 20 email messages 5 minutes ago. the screen will display 20 (see attachment). Now, 3 more messages have arrived, the web page should update the number to 23.
Facebook has similar concepts when our friends like/comment message. The notification changes. Same thing is true on social media game. Any status changes on our game, it will reflect it.
I kind of have idea on how to do it cosmetically (on CSS). How to do it using javascript/asp.net. Do I need to postback in order to refresh the message. I never pay attention to that on facebook/yahoo email/social media games. All I know is something is happening, the webpage is updating the status.
Sorry the question is too broad. If someone can help me to point to the right direction, I appreciate any help
HTML5 introduced a very interesting concept call Server-Sent Events in which server can dynamically connect to the client and send data.
Eg:
var source = new EventSource("demo_sse.asp");
source.onmessage = function(event) {
document.getElementById("result").innerHTML = event.data + "<br>";
};
And on server side you can write,
<%
Response.ContentType = "text/event-stream"
Response.Expires = -1
<!--Writing "data:" is important-->
Response.Write("data: The server time is: " & now())
Response.Flush()
%>
However, some old browsers may not support this.
One other way to accomplish this task is to use Ajax call as,
function checkNewMessages(totalMessages){
return $.ajax({
url: 'demo.asp',
type: 'GET',
cache: false,
data: {
totalMessages: totalMessage;
}
});
}
checkNewMessages(totalMessages).success(function (data) {
// display the data wherever you want
});
//Checking for new messages every 5 seconds
setInterval(checkNewMessages(totalMessages,5000));
Whatever you write within your Write() in server side will be displayed here. Now to constantly check for the new messages you can call the above ajax function with the help of setInterval()
There are many ways to do this, depending on how real time you need it to be.
The most common way is to use JavaScript with an XmlHttpRequest to call an ASP.NET page which returns the number of messages, I recommend you use a JSON object for this. The benefit of this approach allows you to request data from the server without the user experiencing a full page refresh. You can use JavaScript to set it to call every x seconds depending on your requirements.
Collectively that is known as AJAX, using a JavaScript library such as JQuery can make this much easier.
I have recently started to look at inter-browsers communications, and got paricularly interested in webRTC. I am trying at the moment to build a file transfer through a Data Channel with the beginner oriented library provided here :
https://github.com/muaz-khan/WebRTC-Experiment/tree/master/DataChannel .
My application is visible here : https://shirase-ttt.jit.su/Dropzone.html
It does a basic file transfer on drop of a file. The problem is, it works between 2 tabs of your own browser (Chrome tested only, but different locations). But as soon as you try it between 2 different internet connections/locations, it stop working. The channel is established but the file isn't sent. I have no idea where I should start looking, the code seems fine, as it works locally (test yourself, see steps below) but I can't swear I haven't made a mistake, would anybody help?
Steps for testing :
Open https://shirase-ttt.jit.su/Dropzone.html on 2 tabs of your browser / 2 browsers.
Tab1 creates a channel name and clicks Connect.
Tab2 enters the same channel name and clicks join.
After a few seconds, you should see all the Channel info in the console. From this point on, you can drop a small file in the box of any client, and see it downloading through the console of the second client. I use a ~100kb image, which takes about 15seconds to dl. It is quite impressive.
I then tested with a friend remotely. After establishing the channel. You see the file being sent, but nothing is received.
The code :
Client : https://github.com/xShirase/RTC-Exploring/blob/master/Dropzone.html
Server : https://github.com/xShirase/RTC-Exploring/blob/master/ttt.js
on the server, only lines 1-34 are relevant, the rest is for different works. Yes, I have tried stripping it naked. No, it doesn't change anything.
Any ideas are welcome. Thanks. I'm thinking it may be an issue with the hosting, maybe https redir messing up things? I don't know, to be honest. Which is why I write here.
Also, I have another request. The web is at the moment undergoing a revolution in many ways. we have the chance to find ourselves at the very beginning of the curve, where everything is still to do, but enough is done to have some fun. So I'd like to put up a team of people, not professionals, but who are eager to learn as much as they can and do as much as they can to push in the right direction. The point I'm personally at is : Good understanding of sockets, good scripting skills, not pro enough I guess, and lots of ideas. I wanna explore webRTC, understand it properly as it evolves, and participate to this evolution. I'm sure I'm not the only one, so to anyone interested and with similar motivations, let's learn faster by working in groups. Contact me.
Disclaimer : The second part of this post may not be in the right website, I'm not sure. But it's where it can be seen, and that's what I'm looking for. Nothing professional or any obligations of any kind, just code, test ideas, that sort of things. If anyone has issues with that part, edit, flag, downvote, or maybe talk first ;-)
Thanks.
It is NAT traversing issue. DataChannel.js used "only" STUN. Now, it is fixed because using two TURN servers, too. If it is still failing for your; try to use "your own" TURN server.
STUN = {
url: !moz ? 'stun:stun.l.google.com:19302' : 'stun:23.21.150.121'
};
TURN1 = {
url: 'turn:73922577-1368147610#108.59.80.54',
credential: 'b3f7d809d443a34b715945977907f80a'
};
TURN2 = {
url: 'turn:webrtc%40live.com#numb.viagenie.ca',
credential: 'muazkh'
};
iceServers = {
iceServers: options.iceServers || [STUN]
};
if (!moz && !options.iceServers) {
iceServers.iceServers[1] = TURN1;
iceServers.iceServers[2] = TURN2;
}
I need users to be able to post data from a single page browser application (SPA) to me, but I can't put server-side code on the host.
Is there a web service that I can use for this? I looked at Amazon SQS (simple queue service) but I can't call their REST APIs from within the browser due to cross origin policy.
I favour ease of development over robustness right now, so even just receiving an email would be fine. I'm not sure that the site is even going to catch on. If it does, then I'll develop a server-side component and move hosts.
Not only there are Web Services, but nowadays there are robust systems that provide a way to server-side some logic on your applications. They are called BaaS or Backend as a Service providers, usually to provide some backbone to your front end applications.
Although they have multiple uses, I'm going to list the most common in my opinion:
For mobile applications - Instead of having to learn an API for each device you code to, you can use an standard platform to store logic and data for your application.
For prototyping - If you want to create a slick application, but you don't want to code all the backend logic for the data -less dealing with all the operations and system administration that represents-, through a BaaS provider you only need good Front End skills to code the simplest CRUD applications you can imagine. Some BaaS even allow you to bind some Reduce algorithms to calls your perform to their API.
For web applications - When PaaS (Platform as a Service) came to town to ease the job for Backend End developers in order to avoid the hassle of System Administration and Operations, it was just logic that the same was going to happen to the Backend. There are many clones that showcase the real power of this strategy.
All of this is amazing, but I have yet to mention any of them. I'm going to list the ones that I know the most and have actually used in projects. There are probably many, but as far as I know, this one have satisfied most of my news, whether it's any of the previously ones mentioned.
Parse.com
Parse's most outstanding features target mobile devices; however, nowadays Parse contains an incredible amount of API's that allows you to use it as full feature backend service for Javascript, Android and even Windows 8 applications (Windows 8 SDK was introduced a few months ago this year).
How does a Parse code looks in Javascript?
Parse works through classes and objects (ain't that beautiful?), so you first create a specific class (can be done through Javascript, REST or even the Data Browser manager) and then you add objects to specific classes.
First, add up Parse as a script tag in javascript:
<script type="text/javascript" src="http://www.parsecdn.com/js/parse-1.1.15.min.js"></script>
Then, through a given Application ID and a Javascript Key, initialize Parse.
Parse.initialize("APPLICATION_ID", "JAVASCRIPT_KEY");
From there, it's all object manipulation
var Person = Parse.Object.extend("Person"); //Person is a class *cof* uppercase *cof*
var personObject = new Person();
personObject.save({name: "John"}, {
success: function(object) {
console.log("The object with the data "+ JSON.stringify(object) + " was saved successfully.");
},
error: function(model, error) {
console.log("There was an error! The following model and error object were provided by the Server");
console.log(model);
console.log(error);
}
});
What about authentication and security?
Parse has a User based authentication system, which pretty much allows you to store a base of users that can manipulate the data. If map the data with User information, you can ensure that only a given user can manipulate specific data. Plus, in the settings of your Parse application, you can specify that no clients are allowed to create classes, to ensure innecesary calls are performed.
Did you REALLY used in a web application?
Yes, it was my tool of choice for a medium fidelity prototype.
Firebase.com
Firebase's main feature is the ability to provide Real Time to your application without all the hassle. You don't need a MeteorJS server in order to bring Push Notifications to your software. If you know Javascript, you are half way through to bring Real Time magic to your users.
How does a Firebase looks in Javascript?
Firebase works in a REST fashion, and I think they do an amazing job structuring the Glory of REST. As a good example, look at the following Resource structure in Firebase:
https://SampleChat.firebaseIO-demo.com/users/fred/name/first
You don't need to be a rocket scientist to know that you are retrieve the first name of the user "Fred", giving there's at least one -usually there should be a UUID instead of a name, but hey, it's an example, give me a break-.
In order to start using Firebase, as with Parse, add up their CDN Javascript
<script type='text/javascript' src='https://cdn.firebase.com/v0/firebase.js'></script>
Now, create a reference object that will allow you to consume the Firebase API
var myRootRef = new Firebase('https://myprojectname.firebaseIO-demo.com/');
From there, you can create a bunch of neat applications.
var USERS_LOCATION = 'https://SampleChat.firebaseIO-demo.com/users';
var userId = "Fred"; // Username
var usersRef = new Firebase(USERS_LOCATION);
usersRef.child(userId).once('value', function(snapshot) {
var exists = (snapshot.val() !== null);
if (exists) {
console.log("Username "+userId+" is part of our database");
} else {
console.log("We have no register of the username "+userId);
}
});
What about authentication and security?
You are in luck! Firebase released their Security API about two weeks ago! I have yet to explore it, but I'm sure it fills most of the gaps that allowed random people to use your reference to their own purpose.
Did you REALLY used in a web application?
Eeehm... ok, no. I used it in a Chrome Extension! It's still in process but it's going to be a Real Time chat inside a Chrome Extension. Ain't that cool? Fine. I find it cool. Anyway, you can browse more awesome examples for Firebase in their examples page.
What's the magic of these services? If you read your Dependency Injection and Mock Object Testing, at some point you can completely replace all of those services for your own through a REST Web Service provider.
Since these services were created to be used inside any application, they are CORS ready. As stated before, I have successfully used both of them from multiple domains without any issue (I'm even trying to use Firebase in a Chrome Extension, and I'm sure I will succeed soon).
Both Parse and Firebase have Data Browser managers, which means that you can see the data you are manipulating through a simple web browser. As a final disclaimer, I have no relationship with any of those services other than the face that James Taplin (Firebase Co-founder) was amazing enough to lend me some Beta access to Firebase.
You actually CAN use SQS from the browser, even without CORS, as long as you only need the browser to send messages, not receive them. Warning: this is a kludge that would make my CS professors cry.
When you perform a GET request via javascript, the browser will always perform the request, however, you'll only get access to the response if it was from the same origin (protocol, host, port). This is your ticket to ride, since messages can be posted to an SQS queue with just a GET, and who really cares about the response anyways?
Assuming you're using jquery, your queue is https://sqs.us-east-1.amazonaws.com/71717171/myqueue, and allows anyone to post a message, the following will post a message with the body "HITHERE" to the queue:
$.ajax({
url: 'https://sqs.us-east-1.amazonaws.com/71717171/myqueue' +
'?Action=SendMessage' +
'&Version=2012-11-05' +
'&MessageBody=HITHERE'
})
The'll be an error in the console saying that the request failed, but the message will show up in the queue anyways.
Have you considered JSONP? That is one way of calling cross-domain scripts from javascript without running into the same origin policy. You're going to have to set up some script somewhere to send you the data, though. Javascript just isn't up to the task.
Depending in what kind of data you want to send, and what you're going to do with it, one way of solving it would be to post the data to a Google Spreadsheet using Ajax. It's a bit tricky to accomplish though.Here is another stackoverflow question about it.
If presentation isn't that important you can just have an embedded Google Spreadsheet Form.
What about mailto:youremail#goeshere.com ? ihihi
Meantime, you can turn on some free hostings like Altervista or Heroku or somenthing else like them .. so you can connect to their server , if i remember these free services allows servers p2p, so you can create a sort of personal web services and push ajax requests as well, obviously their servers are slow for free accounts, but i think it's enought if you do not have so much users traffic, else you should turn on some better VPS or Hosting or Cloud solution.
Maybe CouchDB can provide what you're after. IrisCouch provides free CouchDB instances. Lock it down so that users can't view documents and have a sensible validation function and you've got yourself an easy RESTful place to stick your data in.