I'm fairly new to MVC and web programming at all. I need to solve one problem.
Let's say I have complete and working mvc app, web services (it might be anything - wcf, servicestack, web api...) and mobile apps (iOS, Android) working with my web service. Now when I'm on my Admin page is there a way for me update this admin page without having to reload it in response to web service requests when my mobile clients send one.
I don't want to ask my database for changes every few seconds though. I really want this flow:
I'm looking at my admin page -> Mobile app is sending a request (for example if user clicked a button or changed position) -> Web service gets the request -> ???? -> Data on my admin page changes.
Edit: Ok. Why it's always like this ? You look for an answer for long time. Then you ask a question and few minutes later you find possible solution. What I've already found is server side js events, websockets and long polling. Am I heading in the right direction?
For ServiceStack you can get real-time updates with Server Events. You can use the C#/.NET ServerEvents Client with Xamarin.iOS and Xamarin.Android to handle Server Push events on iOS and Android.
I think what you might be looking for is http://signalr.net/
Related
I am hoping this is not too off topic for a post here.
I have an asp.net webAPI service, which provides a number of routes to get near realtime data (ie within say 10 seconds), which required the client application to poll for changes.
I am investigating on which technology would be best to add an "opt in" push notification service, which just pushes "thin" payloads to tell the client application it is now time to call the existing REST route for an update. This way, the push payload is small, and does not contain any security sensitive data (it still gets this using the existing REST security infrastructure)
Cloud based messaging
Previously, I have been told that, for a Mobile application, I should use something like Firebase cloud messaging, or some other messaging service, however this does not seem like the right solution for "subscription based notifications" I am talking about here. I can certainly see this would be useful, if the client is on either iOS or Android device, and wanted messages/notifications/alarms (etc), which could also work when the application is not running, but this does not seem like the right thing to use of these notifications of changed data (which may be happening all the time, sometimes every 5 seconds). Also, I do not want to only target these mobile devices, but also, for example either a web or desktop application, which may also use the same REST service
Other technologies
I have seen mention of Web sockets, or, in the case of asp.net, the option to use SignalR (which will wrap the web sockets, with fallback). SignalR looks good, but my worry is the availability of client libraries for non web / Windows applications (eg iOS, Android). I am also looking at Rest Hooks. These look interesting, but I can't quite see what the actual "push mechanism" is; it almost looks like they need to POST to the subscriber using HTTP, which means the subscriber has to also act as a "server endpoint".
Just after any thoughts / best practices on this, or what others have used?
In particular, (the verification or otherwise), that for this use case, using cloud based messaging is not the right thing to use due to the frequency of these push notifications (ie something where my server gets to the application via another 3rd party service which pushes to the device/application)
Thanks in advance for any suggestions!
Signalr is an option
There are some libraries which you can use in iOS and android. I suggest you to read once https://visualstudiomagazine.com/articles/2013/11/01/how-to-use-signalr-in-ios-and-android-apps.aspx (its a bit older, but on the point)
Android Client: See How to use signalr in Android
Some alternatives :
Pusher (https://pusher.com/)
Android Client: https://pusher.com/docs/android_quick_start
iOS Client: https://pusher.com/docs/ios_quick_start
Socket.IO (https://socket.io/)
Details iOS Client: https://socket.io/blog/socket-io-on-ios/
Details Andriod Client: https://github.com/socketio/socket.io-client-java
To discuss:
Why you will only send a thin payload whith signalr? I see no benefit for that.
Why "using cloud based messaging is not the right thing"? I do not understand your arguments but I do not know how your application looks like.
I have two different web applications that need to communicate with each others (which I can currently accomplish by using Silverlight Duplex but that doesn't scale very well). After reading about SignalR, I'd like to give this a try but failed to find much documentation on how to do this. Any advice on ho to get started would be greatly appreciated.
Thanks!
More specific Info:
Example:
Application A (Bidding Interface) - A web page to allow multiple end-users to place bids on certain items.
Application B (Managing Interface) - A web page to allow a user (or could potentially be multiple users) to monitor/control the actions from Bidding Interface.
So when a user from Application A place a bid on a piece, I'll need a way to alert Application B that a bid has been placed. Then from Application B, should the user choose to accept the bid, I need to send an alert back to Application A (to update current price, increase bid etc...)
In all honesty, in might just be simpler to have each application push the notifications to each other via standard service calls (WCF, ASMX, HTTP handler endpoints, MVC controllers, whatever). SignalR is useful in browser to server communications because there isn't a consistent way to do push from the server to a connected browser. But from web app to web app pushing is simple; Application A just calls a service endpoint on Application B to notify it of something happening.
Assuming that what you want is something like ...
User (browser) --- Application A --- Application B --- User (Browser)
Realtime communication can be done by doing the following ...
This isn't the job of signalR however something like NServiceBus would fit this very well.
you reference a bus dll file and hubs can both raise and respond to events.
In your case you would have both SignalR and your Service Bus technology work together to allow the cross application sync.
So the process is something like ...
User in application A fires up browser and requests page.
Application A creates Hub instance which internally subscribes to Service Bus events
User in application B fires up browser and requests page.
Application B creates Hub instance which internally subscribes to Service Bus events
User on either application does some action resulting in SignalR picking up a message.
SignalR raises bus event to say "This user did something" on the service bus.
Other Hub on other Application through subscribription to the event gets notified of the event and takes any action to inform its connected users of it.
Lesson to be learnt here ...
Don't try and make a technology do something beyond its purpose ... use the right tool for the job.
This entire solution can be done with little more than about 20 lines of code after getting the core framework setup.
NServiceBus can be found here:
http://particular.net/nservicebus
Disclaimer: There may be other solutions but this one suggestion don't assume this is the only way this can be solved, and the only technologies that be used in this manner.
I am not affiliated in any way with Particular or the NServiceBus product.
We have a window application and a web application, and both connect to a same database to handle data. User on web application will do some changes and wait for the approve from users on window application. Is there any way to show a live update or notification on web application whenever an approve is made at window application which is lead to change in database?
Note: we use ASP.NET for web application and .NET for windows application
This link which talks about SQLDependency and Query Notification seems to be what you are looking for.
You could setup a "notification" area within an updatepanel, or just use straight up ajax to make queries to the database on a specified interval as well.
There are several options.
you can refresh your ASP.NET page by regular interval. http://www.devcurry.com/2009/03/how-to-refresh-aspnet-gridview.html
Refresh a portion of the page periodically using AJAX. I would use jquery for the ajax stuff: jquery.com
Not sure how long the approval process is expected to take, but you could set the page to poll the server every 5 seconds, 15 seconds, whatever makes sense. If it's just refreshing a small portion of the page, it shouldn't be too much of a burden on the server relative to reloading the entire page at every interval.
How do you send data from an ASP.NET web application to a windows form application?? How do you establish the connection? I looked up webrequest/webresponse/post but i think thats only if you want to communicate between 2 asp.net web applications.
You might use a socket.
It would help if you're more specific about exactly what you're trying to accomplish. Do you need live communication, or would connecting to a shared database do what you need? Is the web application on the same computer as the server or a different one from the forms application?
Update:
If you're trying to pass messages to the Windows Form without using or implementing any sort of protocol, you might look into how to use LISTEN/NOTIFY on PostgreSQL. You could then just add data to a table, then have the forms application consume the data. This would have the added benefit that your forms app wouldn't have to miss any data if it was not on.
My opinion to you is to implement a webservice. I made a project for mobile devices using webservices, the mobiles had an application made in winforms that call a webmethod that made an action which was registered in the system. A web page showed the data and the events of every mobile device.
If you need an explantation of webservices you can go here.
The strategy in your case would be to implement the Observer Pattern or to raise an event to make the application or winform to be noticed about a change or action in the web page.
Is it possible to embed an external application inside the browser (IE, Chrome, Safari, Firefox) so it will look like a native web application but actually having access to the USB ports of the client machine? I have heard that I need to make an ActiveX control. I would like to use the .Net framework, but if that is not possible, maybe using Java or C++ will be fine.
I have to make an application that will allow to the users to connect an external device to an USB port, this device will take a backup of the information contained in a SIM card and send it to the user's account online agenda. So the user can restore it later using the same application. This should be a web application or at least look like one.
If the first is not possible. Is there any way to launch an external application from all the browsers, and then pass information to the browser window to allow it to refresh after the backup has been made?
Thanks for your help in advance.
First off this seems to be a big security issue and hence this is the reason why you might be finding it tricky.
What I would do is look at it from a different angle; what am I trying to achieve? How is the user going to use the data? Where is the user going to use the data?
From you question I have answered those questions with the following; I hope I've not miss interpretted anything.
I want to copy the data from an external sim card to a central location
I want the user to see this data from the central location; preferablly from a web application.
The user is going to see and use the data from the web app
Assuming all of these things are true; one design option is the following:
1 - Have a client based application which can read stuff from the usb device
2 - Have a secure webservice which the client based application can upload the data too
3 - Have a web application which can view this data and see refreshes
Let me go into bit more detail for each step.
1 - If you write a small client application it is installed or at least runs on the client computer. Due to this it can access the local client resources such as usb and interface with them. This will mean they can read the sim data throuogh this app, buut also potentially save it locally as well as upload the data. To access the web service they would enter their username/password so you could authenticate them for the upload.
2 - This web service would do the authentication from the client application, but also receive the data submitted from the client app. Acessing web services from .net now a days is really straight forward. Using this web service the client application could also do some checking to make sure the data has been updated and it could handle re-tries if the network dropped etc.
3 - The web front end of the system would interface to the same data source. This site would take the username / password to authenticate them on the site, but also let them see the uploaded data. As for the refreshes; if the user is logged in and looking at the data you could have a javascript timer polling an action/service to see when new records have been added etc. This could then display a message through jQuery or similar to notifiy the user. This could be similar to the notifications which StackOverflow gives when you visit for the first time or get a new badge etc.
Hope this helps :-)