I Have created an application one is web and another is console.
On web all the users are connected to a hub.
On console application I connect to the web and hub and start message. It works fine when I opened my application in 1 web browser.
In my console.
var hubConnection = new HubConnection("http://192.168.1.160:1000/");
var chat = hubConnection.CreateHubProxy("MyHub");
hubConnection.Start().Wait();
chat.Invoke("NotifyAllClients", "Hello").Wait();
It works very well. I opened the web application (http://192.168.1.160:1000/) use the javascript client libraries for SignalR and connect successfully.
Then run the console, it shows the message from console to web. Perfect.
Not I face issue with another case.
When I open the same application in multiple browser
Console will not working. it hung up at line
hubConnection.Start().Wait(); // Console hang there...
How I send the message to all of the users? Any solution.
Problem 2
When I run the console and refresh the web application. Browser not load the web page. Where is the problem.
Problem 1: I cannot reproduce that behaviour, what are you expecting to see? Is it that you're not seeing the messages on the console client? I can open up the JS client in multiple browsers and fire up the console client multiple times without problems.
Problem 2: If you've fired up your console, that means you've sent the message Hello and (depending on your hub implementation) the hub has broadcasted the message. Now if you refresh your web page, it cannot know about this message unless you persist the messages within the hub. If you do, you could re-sent the messages upon connection of the client (which is what happens when you refresh your browser client).
Related
I am using SignalR in a Blazor server-side app. I added the Microsoft.AspNetCore.SignalR.Client Nuget package (v5.0.11) to the project, and used the following code to create the hub connection...
HubConnection hubConnection = new HubConnectionBuilder()
.WithUrl("url")
.Build();
await hubConnection.StartAsync();
I then send out a message with the following code (Debug.WriteLine added to confirm what's going on)...
Debug.WriteLine($"{DateTime.Now.ToLongTimeString()} SignalR msg sent");
await hubConnection.SendAsync("Send", "Hello");
The component that is to handle such messages creates the hub connection and hooks up to the On handler as follows...
HubConnection hubConnection = new HubConnectionBuilder()
.WithUrl("url")
.Build();
hubConnection.On<string>("Receive", msg =>
Debug.WriteLine($"{DateTime.Now.ToLongTimeString()} SignalR msg received - {msg}"));
await hubConnection.StartAsync();
When the message is sent out, it is definitely only being sent once (which I can confirm from the output panel, where I only see the "sent" output once), but it is received twice.
Searching around, it seems that a common reason for this is if jQuery was loaded twice. However, I have checked this, and it's not the case. It's only being loaded the once. Furthermore, one of the other developers on the team tried it, and he got the message received 15 times! Even if we had accidentally included jQuery twice, we certainly didn't include it 15 times. Also, he's using exactly the same code as me (checked out from source control), so we should get the same results if this were the issue.
Anyone any idea why this could be happening? Thanks
This can occur when you initialise a HubConnection within a component and don’t configure IDispose or IAsyncDispose on your component to dispose the HubConnection.
In a Blazor Server-Side application there is already a SignalR host pushing updates to the client.
If you want to push updates from a page you can use a Singleton Service to handle the communication.
If you set up your own SignalR hub and use the SignalR client in your components, your application is something like the diagram below:
As you can see, the client is actually running on the server. The SignalR hub you've added adds processing and memory overhead and does not add any value.
I created a simple sample app that uses a service that clients listen to for updates:
https://github.com/conficient/BlazorServerWithSignalR
I am researching to use signalr to send messages from an api to a specific user (keyword). Locally, I have everything working as designed (even using redis backplane).
When I move up to an actual environment with multiple servers (azure app service), it seems like messages to specific users don't flow through the backplane. If I send a message to Clients.All it works. But, if I send a message to Clients.User(username), the message is never received. This works locally because it's a single server, but doesn't seem to work in multiple servers.
await this.impersonationContext.Clients.User(mainUserName).SendAsync("msguser", new object[] { mainUserName });
await this.impersonationContext.Clients.All.SendAsync("msg", new object[] { "wtf" });
If I call the above code, only the msg event is fired, but the msguser is never recieved.
Could I be missing something on the setup? That's my assumption, I cannot be the only one doing this.
Below is my setup in the startup.cs. This is using .net core 5 with the latest nugets, etc
services.AddSignalR(options =>
{
options.EnableDetailedErrors = true;
})
.AddStackExchangeRedis(this.Configuration["Redis:Cache"], options => {
options.Configuration.ChannelPrefix = "ImpersonationService";
});
services.AddSingleton<IUserIdProvider, NameUserIdProvider>();
Any help would be appreciated.
Update #1
Looks like the user info is being pushed through the backplane (username hidden). So maybe its the connection from javascript client?
Update #2
Getting closer...looks like the subscription isn't setup for the specific user like I see locally. Could this be websockets?
Update #3
Found it....sorta.
I was missing the authorize attribute on the hub, which was allowing the websocket to connect, even though websockets isn't authenticating for some reason (different issue). Once I added the authorize, it will drop down to long polling with the user info and works as designed
I'm playing with different ways to create push notifications in asp.net core, since my boss asked me to research it.
So i just set up a barebones project that uses signalr to send messages from a hub to the client, and conversely for the client to the hub.
Currently, I have a button on a certain page where this javascript is used:
function receive() {
$.ajax({
url: '/msg/SendToClient',
type: 'get',
});
}
var connection = new signalR.HubConnectionBuilder()
.withUrl("/NotificationHub")
.build();
connection.on("ReceiveMessage", function (user, message) {
alert(message);
});
connection.start();
Where the receive() is called everytime the button is pushed, that means that a corresponding controller action is called, which sends a message from server -> client.
But what I want is that I would like the javascript file to be laying on the client, and just run once in a while to check for new available push notifications.
A few scenarios are available, and I would like to know about all of them:
Push notifications when browser is closed. I'm guessing this is not possible with a "regular" service worker?
Push notification when browser is open, but site is not open. For this, I guess I will need to somehow have a javascript file/service worker on the clients computer just always running. This I really have no idea how to achieve this.
A push notification that can work when the site is open in the browser. All I think I need for this is to have the javascript included always when the user is on the site, and then somehow make a request every few minutes.
Any inputs on these three things will be greatly appreciated. Is any of them easily achieveable/advisable? Is there any "normal" mode of operation for these three approaches to push notifications?
For any of these three scenarios, is there a case where signalr is parhaps not the best resource?
I have a MVC web application and a console application created as a separate project inside my web application. I want this console application to be run as a windows service at specified intervals. The console application is for sending mail to some persons. I need to include my application URL in the mail content body which redirect to my application login page. Since i am running this service for more than one instance i could't hard code the URL in code. Someone please help. I tried the below code. But it is returning null value.
var site = HttpContext.Current.Request.Url.Scheme + "://" + HttpContext.Current.Request.Url.Authority + HttpContext.Current.Request.ApplicationPath.TrimEnd('/');
var url = string.Format("<a href='{0}'>Login</a>", site);
I converted this from the comment to the question.
You are trying to obtain information from HttpContext.Current in situation when there is no HttpContext available at all - because your console application is launched directly by the operating system and not on the event of incoming http request (as oposed to request handling in your MVC application) - so there simply is no http context to use (hence HttpContext.Current is null in your console application).
You have to establish your own application logic for your console application that determines which URL to use in your emails. What would that be depends on the answer to the question "what does the url to be used in each email depend on specifically"? In other words - "how should each email know what URL to use"? Once you figure out the answer to that question then you can think of how to pass that dependency to your windows service.
Example (I do not know if it describes your case):
there are several web applications on different URLs
each of these web applications can add email to the queue to be send
windows service (console app) is scheduled to run once in a while and process the queue by sending the emails. Each email has to have an URL of the application from where it was added.
Assuming the example above you can just add the email together with the URL of the application to the queue (insted of just the email) and then retrieve that information from the queue in your console application. So then each of the emails has associated URL. It is irrelevant how would the queue itself be implemented (SQL, file, ...).
I am using SignalR (with cross-domain request), version 2.3.0 for webchat integrated to ASP.NET site. Everything is working fine. But I found strange behaviour of SignalR connection. When I clicked to the reference from tab of the chat for file downloading SignalR connection was aborted and onDisconnected method was triggered in my Hub class. FireBug show me next POST-request:
http://*:81/signalr/abort?transport=longPolling&clientProtocol=1.4&token=eUpLNitKcmR1d2JhTTRvcHNVZmEwcG1EKzYvMElZbmg4aE5yam9xM3k0dz0_IjAsNGJmOWNhODUtNDU2NS00NWExLWFjMTgtNzgyN2FhZDA2Njg1LGxvY2FsaG9zdCI1&State=1&connectionToken=hDXe9xIZtmrapjl1LRwtK9B%2BfYMoeuHka8ctBLaPa0YnjiN9iiFa%2BvFMBHIGpGH0h8qPEDgGZSRGwjMw3Wm1DJi6cUPtZjLca6%2FR2576SGksLAj3lnPN1JWIlxMsn8%2Bf&connectionData=%5B%7B%22name%22%3A%22c%22%7D%2C%7B%22name%22%3A%22voip%22%7D%5D, where * is my domain.
It is reproduced in Mozilla Firefox (version 30.0) for LongPolling or Websocket transports. How I can fix this problem? Or is it bug of SignalR or Firefox?
This bug has been recently filed against SignalR on GitHub. The basic idea is that downloading a file causes Firefox to trigger the window.onbeforeunload event which in turn causes SignalR to close any ongoing connections.
For now, the workaround is to attach a handler to the client's disconnected event that will call $.connection.start again after a short window.setTimeout.
You could also unbind SignalR's onbeforeunload handler: $(window).unbind("beforeunload"). The downside of doing this is that Firefox might not gracefully disconnect when the user leaves the page running SignalR. Without a graceful disconnect, SignalR will wait over 30 seconds before it times out the client and calls the OnDisconnected handler on the Hub or PersistentConnection.
I have managed to use the workaraound explained by halter73 and I have solved the issue described by dudeNumber4 resetting the connectionid inside the disconnect event so that the server kept calling back the right users based on their connectionid without the need to address them by their user or group names.
$.connection.hub.disconnected(function () {
setTimeout(function () {
$.connection.hub.start().done(function () {
$("#mySignalRConnectionIdHidden").val($.connection.hub.id);
});
}, 3000);
});