I have an ASP.NET MVC application presenting some data and I want it to
open a new tab, or
redirect to a new view
when a web service gives me a signal. This WS is supposed to handle some external data and requests and when some specific action is called, I want it to be able to give my web application some kind of signal.
I was thinking about using Html.Action to an asynch controller but then I don't know how to provide the signal from the WS to the controller (or all instances of them).
Hopefully, it is understandable. Do you have an idea what needs to be done?
Thanks in advance.
So basically your problem comes down to the fact that server state is changed (through WS) and we want to make something happen at the client side where the your web app is being viewed.
Frankly it's not straightforward. Internet works on the Client -> Server architecture. User sends a request to the server, server responds. What you are trying to do is reverse of it. You want to send a request from server to user. HTTP protocol doesn't work like that.
Right now, to do something similar following two strategies are used:
Websockets : try searching them on google. You create a socket between the client and server and once server gets updated by the WS, it sends a request to the client through the socket. You can ask it to navigate to a different view or open a new window. The downside with it is that its not supported by the majority of the browsers. Might take a year or so to be. Not really recommend now.
Polling : You can make Ajax requests from your browser to server in certain intervals (you know like every 5 seconds) and see if the server state has changed or now. If yes, then do your stuff. That's the most common technique. Twitter.com uses it. There is also another version of it called Comet or Long Polling but I won't confuse you with that.
The important thing to note here is that whatever you want to do (open tab, change view etc) you have to do it through Javascript at the client side.
hope that helps
Related
Here is my need:
I have to displays some information from a web page.
The web browser is actually on the same machine (localhost).
I want the data to be updated dynamically by the server initiative.
Since HTTP protocol is actually a request/response protocol, I know that to get this functionality, the connection between the server and the client (which is local here) should be kept open in some way (Websocket, Server-Sent Events, etc..)
Yes, "realtime" is really a fashion trend nowadays and there are many frameworks out there to do this (meteor, etc...)
And indeed, it seems that Rails supports this functionnality too in addition to using Websockets (Server-Sent Events in Rails 4 and ActionCable in Rails 5)
So achieving this functionnality would not be a big deal, I guess...
Nevertheless what I really want is to trigger an update of the webpage (displayed here locally) from a request made by another client..
This picture will explain that better :
At the beginning, the browser connects to the (local) server (green arrows).
I guess that a thread is executed where all the session data (instance variables) are stored.
In order to use some "realtime" mechanisms, the connection remains open and therefore the thread Y is not terminated. (I guess this is how it works)
A second user is connecting (blue arrows) to the server (could be or not be the same web page) and make some actions (eg. posting a form).
Here the response to that external client does not matter. Just an HTTP OK response is fine. But a confirmation web page could also be returned.
But in anyway the thread X (and/or the connection) has no particular reason to be kept.
Ok, here is my question (BTW thank you for reading me thus far).
How can I echo this new data on the local web browser ?
I see 2 differents ways to do this :
Path A: Before terminating, the thread X passes the data (its instance variables) to the thread Y which has its connection still open. Thus the server is able to update the web browser.
Path B: Before terminating the thread X sends a request (I mean a response since it is the server) directly to the web browser using a particular socket.
Which mechanisms should I use in either method to achieve this functionnality ?
For method A, how can I exchange data between threads ?
For method B, how can I use an already opened socket ?
But which of these two methods (or another one) is actually the best way to do that?
Again thank you for reading me thus far, and sorry for my bad english.
I hope I've been clear enough to expose my need.
You are overthinking this. There is no need to think of such low-level mechanisms as threads and sockets. Most (all?) pub-sub live-update tools (ActionCable, faye, etc.) operate in terms of "channels" and "events".
So, your flow will look like this:
Client A (web browser) makes a request to your server and subscribes to events from channel "client-a-events" (or something).
Client B (the other browser) makes a request to your server with instructions to post an event to channel "client-a-events".
Pub-sub library does its magic.
Client A gets an update and updates the UI accordingly.
Check out this intro guide: Action Cable Overview.
I am working in a Rails application and below is the scenario requiring a solution.
I'm doing some time consuming processes in the background using Sidekiq and saves the related information in the database. Now when each of the process gets completed, we would like to show notifications in a separate area saying that the process has been completed.
So, the notifications area really need to pull things from the back-end (This notification area will be available in every page) and show it dynamically. So, I thought Ajax must be an option. But, I don't know how to trigger it for a particular area only. Or is there any other option by which Client can fetch dynamic content from the server efficiently without creating much traffic.
I know it would be a broad topic to say about. But any relevant info would be greatly appreciated. Thanks :)
You're looking at a perpetual connection (either using SSE's or Websockets), something Rails has started to look at with ActionController::Live
Live
You're looking for "live" connectivity:
"Live" functionality works by keeping a connection open
between your app and the server. Rails is an HTTP request-based
framework, meaning it only sends responses to requests. The way to
send live data is to keep the response open (using a perpetual connection), which allows you to send updated data to your page on its
own timescale
The way to do this is to use a front-end method to keep the connection "live", and a back-end stack to serve the updates. The front-end will need either SSE's or a websocket, which you'll connect with use of JS
The SEE's and websockets basically give you access to the server out of the scope of "normal" requests (they use text/event-stream content / mime type)
Recommendation
We use a service called pusher
This basically creates a third-party websocket service, to which you can push updates. Once the service receives the updates, it will send it to any channels which are connected to it. You can split the channels it broadcasts to using the pub/sub pattern
I'd recommend using this service directly (they have a Rails gem) (I'm not affiliated with them), as well as providing a super simple API
Other than that, you should look at the ActionController::Live functionality of Rails
The answer suggested in the comment by #h0lyalg0rithm is an option to go.
However, primitive options are.
Use setinterval in javascript to perform a task every x seconds. Say polling.
Use jQuery or native ajax to poll for information to a controller/action via route and have the controller push data as JSON.
Use document.getElementById or jQuery to update data on the page.
I have an MVC application using Razor, html5 and a WCF service. The problem is one WCF service takes a long time to run which means that the user has no indication what the service is doing. I would like to send progress information to the HTML5 client and would like some suggestions over what the best approach would be. All help will be gratefully received…
You could even use SignalR for the Reverse Ajax purpose. If you want to shy away from these heavy framework, and probably want to go with setInterval you can check out this article This article is by Dino Espito, in which talks about how to use setInterval to make repetitive call to server to get the progress. Another one by Dino Espito in which he uses SignalR libarary to make a context sensitive progress bar
For Full Collection of his article on Context Sensitive Progress Bar See here
You have to go for Comet implementation. In the case of Comet or Reverse Ajax the client will send a long duration ajax call to the server and wait for a response. So in your case first the HTML5 client will send a request to the server and wait for the progress information once the WCF service returns some info back the client has to make the again make the long duration call till the process is completed.
There are open-sources available that helps to simplify your work like nComet or PokeIn.
There is also an article available in code project that talks about this approach.
Whenever you request a web page, you send a message to a server, and the server responds. As far as I know, most interaction occurs this way: the client says one thing to the server, and the server says one thing back. The server can't "speak until spoken to".
Are there any technologies that let the server initiate a conversation? For instance, if you had a page that you wanted to always keep up to date, the way I'd do it now is periodically make an AJAX request to get updated info from the server. However, it would be nicer if the server could just let the client know at the moment when new info was available. Is there anything around that can do this?
The concept you are looking for is push technology.
All HTTP interactions are client request, server response. To get away from polling for updates as you described, you would have to look outside of HTTP; to do this in a webpage, you would have to use a plugin, Java applet, ActiveX control, etc.
Trying to figure out a way where I can pass some data/fields from a web page back into my application. This needs to works on Windows/Linux/Mac so I can't use a DLL or ActiveX. Any ideas?
Here's the flow:
1. Application gathers some data and then sends it to a web page using POST that is either imbedded in the app or pops up a new IE window.
2. The web page does some services and then needs to relay the results back to the application.
The only way to do this that I can think of is writing the results locally from the page in a cookie or something like that and have the application monitor for a specific file in that folder.
Alternatively, make a web service that the application hits after passing control to the page and when the page is done the web service will return the data. This sounds like it might have some performance drawbacks.
Can anyone suggest any better solutions for this?
Thanks
My suggestion:
Break the processing logic out of the Web Page into a seperate assembly. You can then create a Web Service that handles all of the processing without needing to pass control over to a page.
Your application can then call the Web Service directly and then serialize the results and work with the data quite easily.
Update
Since the page is supplied by a third party, you obviously can't break anything out. The next best thing would be to handle the entire web request internal to your application (rather than popping a new Window).
With this method, you can get the raw HTTP response (and page markup) and work with it directly. You can then parse the Response stream and gather the required data from it.
During performing an HTTP request you should be able to retrieve the text returned by the page. For instance, if your HTTP POST was to hit a Java servlet, the doPost() method would be fired and you would then perform your actions, you could then use the PrintWriter object from the Response object (PrintWriter out = response.getWriter();) and write text back to the calling application. I'm not sure this helps?
The fact that
web page is hosted by a third party
and they need to be doing the
processing on their servers.
is important to this question.
I like your idea of having the app call a webservice after it passes the data to the third-paty web page. You can always call the webservice asynchronously if you're worried about blocking your application while waiting for results from this webservice.
Another option is that your application implements an XML-RPC server that can be called from the web page using PHP, Python or whatever you use to build the website
A REST server will do the job also...