I've got an architectural problem I just can't find a suitable solution for. In my web application based on ASP.NET Core MVC 2.2, I want to pull data from a JWT secured API and publish it to connected clients using SignalR. Furthermore, the data should only be fetched, if at least one client is actually connected to the SignalR hub. My problem: I can't find a way to cancel the Task.Delay inside a while loop, when an additional client's connected. To clarify, let me show you what I came up with so far.
First of all, here's the API client class:
public class DataApiClient : IDataApiClient {
private readonly HttpClient httpClient;
private readonly string dataApiDataUrl;
public DataApiClient(HttpClient httpClient, IOptionsMonitor<DataSettings> dataSettings) {
this.httpClient = httpClient;
dataApiUrl = dataSettings.CurrentValue.dataApiUrl;
}
public async Task<DataOverview> GetData(string accessToken) {
DataOverview dataOverview = new DataOverview();
try {
httpClient.DefaultRequestHeaders.Accept.Clear();
// more httpClient setup
Task<Stream> streamTask = httpClient.GetStreamAsync(dataApiUrl);
dataOverview = serializer.ReadObject(await streamTask) as DataOverview;
} catch(Exception e) {
Debug.WriteLine(e.Message);
}
return dataOverview;
}
}
SignalR hub:
public interface IDataClient {
Task ReceiveData(DataOverview dataOverview);
}
public class DataHub : Hub<IDataClient> {
private volatile static int UserCount = 0;
public static bool UsersConnected() {
return UserCount > 0;
}
public override Task OnConnectedAsync() {
Interlocked.Increment(ref UserCount);
return base.OnConnectedAsync();
}
public override Task OnDisconnectedAsync(Exception exception) {
Interlocked.Decrement(ref UserCount);
return base.OnDisconnectedAsync(exception);
}
}
And a BackgroundService that gets the work done:
public class DataService : BackgroundService {
private readonly IHubContext<DataHub, IDataClient> hubContext;
private readonly IDataApiClient dataApiClient;
private readonly IAccessTokenGenerator accessTokenGenerator;
private AccessToken accessToken;
public DataService(IHubContext<DataHub, IDataClient> hubContext, IDataApiClient dataApiClient, IAccessTokenGenerator accessTokenGenerator) {
this.hubContext = hubContext;
this.dataApiClient = dataApiClient;
this.accessTokenGenerator = accessTokenGenerator;
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken) {
while (!stoppingToken.IsCancellationRequested) {
if (DataHub.UsersConnected()) {
if (NewAccessTokenNeeded()) {
accessToken = accessTokenGenerator.GetAccessToken();
}
DataOverview dataOverview = dataApiClient.GetData(accessToken.Token).Result;
dataOverview.LastUpdated = DateTime.Now.ToString();
await hubContext.Clients.All.ReceiveData(dataOverview);
}
// how to cancel this delay, as soon as an additional user connects to the hub?
await Task.Delay(60000);
}
}
private bool NewAccessTokenNeeded() {
return accessToken == null || accessToken.ExpireDate < DateTime.UtcNow;
}
}
So my questions are:
My main problem: How can I cancel the Task.Delay() inside the ExecuteAsync() while loop the moment an additional user connects, so the newly connected client gets data immediately and doesn't have to wait until the Delay() task is over? I guess, this would have to be placed in OnConnectedAsync(), but calling the service from there doesn't seem to be a good solution.
Is this architecture even good? If not, how would you implement such a scenario?
Is there a better way to keep a count of currently connected SignalR users? I read that a static property in a Hub can be problematic, if more than one SignalR server is involved (but this is not case for me).
Does IHostedService/BackgroundService even make sense here? Since services that get added using AddHostedService() are transient now, doesn't the while loop inside the ExecuteAsync() method defeat the purpose of this approach?
What would be the best place to store a token such as JWT access tokens, so that transient instances can access it if it's valid and update it when it expired?
I also read about injecting a reference to a specific IHostedService, but that seems to be just wrong. Also this discussion on Github made me feel that there has to be a better way to design the communication between SignalR and continuously running services.
Any help would be greatly appreciated.
I have two actors, lets call them ActorA and ActorB. Both actors reside in their own separate process as a Topshelf based Windows Service.
Basically they look like this.
public class ActorA : ReceiveActor
{
public ActorA()
{
this.Receive<ActorIdentity>(this.IdentifyMessageReceived);
}
private bool IdentifyMessageReceived(ActorIdentity obj)
{
return true;
}
}
public class ActorB : ReceiveActor
{
private readonly Cluster Cluster = Akka.Cluster.Cluster.Get(Context.System);
public ActorB()
{
this.Receive<ActorIdentity>(this.IdentifyMessageReceived);
this.ReceiveAsync<ClusterEvent.MemberUp>(this.MemberUpReceived);
}
protected override void PreStart()
{
this.Cluster.Subscribe(this.Self, ClusterEvent.InitialStateAsEvents, new[]
{
typeof(ClusterEvent.IMemberEvent),
typeof(ClusterEvent.UnreachableMember)
});
}
protected override void PostStop()
{
this.Cluster.Unsubscribe(this.Self);
}
private async Task<bool> MemberUpReceived(ClusterEvent.MemberUp obj)
{
if (obj.Member.HasRole("actora"))
{
IActorRef actorSelection = await Context.ActorSelection("akka.tcp://mycluster#localhost:666/user/actora").ResolveOne(TimeSpan.FromSeconds(1));
actorSelection.Tell(new Identify(1));
}
return true;
}
private bool IdentifyMessageReceived(ActorIdentity obj)
{
return true;
}
}
My config files are super simple
ActorA:
akka {
log-config-on-start = on
stdout-loglevel = DEBUG
loglevel = DEBUG
actor.provider = cluster
remote {
dot-netty.tcp {
port = 666
hostname = localhost
}
}
cluster {
seed-nodes = ["akka.tcp://mycluster#localhost:666"]
roles = [actora]
}
}
ActorB:
akka {
log-config-on-start = on
stdout-loglevel = DEBUG
loglevel = DEBUG
actor.provider = cluster
remote {
dot-netty.tcp {
port = 0
hostname = localhost
}
}
cluster {
seed-nodes = ["akka.tcp://mycluster#localhost:666"]
roles = [actorb]
}
}
I now want to identify all the given actors attached to my cluster. I do this by waiting for the cluster node MEMBER UP event and trying to send an Identify() message to the given actor to receive a reference to it.
The problem is that I cannot seem to be able to successfully send the message back to ActorA. Infact when executing the above code (despite the fact that I have the correct reference in the ActorSelection method) the ActorIdentity message is invoked in ActorB rather than ActorA.
I have tried handling all received message in ActorA and it appears I never receive the Identity message. However I can successfully send any other type of message ActorA using the same ActorSelection reference.
So can anyone provide any insight? Why is my identity message never reaching my target actor?
ActorIdentity message is invoked in ActorB rather than ActorA.
This works as intended, as you're sending Identify request from actor B → A, for which ActorIdentity is a response message (send automatically from A → B).
You can already observe this behavior in action, since:
Context.ActorSelection(path).ResolveOne(timeout)
is more or less an equivalent of
Context.ActorSelection(path).Ask<ActorIdentity>(new Identify(null), timeout: timeout)
Identify is a system message, which is handled always before any programmer-defined message handlers are invoked - for this reason you probably won't catch it in your own handlers.
I have a full engine that relies on abstractions based on user interactions. This works great with WPF/Xamarin app, cause I can implements this abstractions with window/form.
I have a little problem for porting this engine into ASP MVC.
A simple example can be show as this.
Abstraction interface (simplified)
public interface IQuestionBox
{
Task<bool> ShowYesNoQuestionBox(string message);
}
For WPF, it's really simple, I implement this interface as return the result of a window by calling ShowDialog().
In a simple business class, I can have this kind of calls (simplified) :
public async Task<string> GetValue(IQuestionBox qbox)
{
if(await qbox.ShowYesNoQuestionBox("Question ?"))
{
return "Ok";
}
return "NOk";
}
I really don't see how can I implement this kind of behavior in ASP, due to stateless of HTTP, knowing that this kind of call can be as various as domain/business need. The way I think it should be done is by returning a PartialView to inject into popup, but I don't see how to do this without breaking all the process ...
Anyone has ever done this ?
as I've said, I strongly doesn't recommend this pratice, but its possible, bellow the code that allows to do it, let's go:
To become it's possible I abused the use from TaskCompletionSource, this class allow us to set manually result in a task.
First we need to create a structure to encapsulate the process:
public class Process
{
// this dictionary store the current process running status, you will use it to define the future answer from the user interaction
private static Dictionary<string, Answare> StatusReport = new Dictionary<string, Answare>();
// this property is the secret to allow us wait for the ShowYesNoQuestion call, because til this happen the server doesn't send a response for the client.
TaskCompletionSource<bool> AwaitableResult { get; } = new TaskCompletionSource<bool>(true);
// here we have the question to interact with the user
IQuestionBox QuestionBox { get; set; }
// this method, receive your bussiness logical the receive your question as a parameter
public IQuestionBox Run(Action<IQuestionBox> action)
{
QuestionBox = new QuestionBox(this);
// here we create a task to execute your bussiness logical processment
Task.Factory.StartNew(() =>
{
action(QuestionBox);
});
// and as I said we wait the result from the processment
Task.WaitAll(AwaitableResult.Task);
// and return the question box to show the messages for the users
return QuestionBox;
}
// this method is responsable to register a question to receive future answers, as you can see, we are using our static dictionary to register them
public void RegisterForAnsware(string id)
{
if (StatusReport.ContainsKey(id))
return;
StatusReport.Add(id, new Answare()
{
});
}
// this method will deliver an answer for this correct context based on the id
public Answare GetAnsware(string id)
{
if (!StatusReport.ContainsKey(id))
return Answare.Empty;
return StatusReport[id];
}
// this method Releases the processment
public void Release()
{
AwaitableResult.SetResult(true);
}
// this method end the process delivering the response for the user
public void End(object userResponse)
{
if (!StatusReport.ContainsKey(QuestionBox.Id))
return;
StatusReport[QuestionBox.Id].UserResponse(userResponse);
}
// this method define the answer based on the user interaction, that allows the process continuing from where it left off
public static Task<object> DefineAnsware(string id, bool result)
{
if (!StatusReport.ContainsKey(id))
return Task.FromResult((object)"Success on the operation");
// here I create a taskcompletaionsource to allow get the result of the process, and send for the user, without it would be impossible to do it
TaskCompletionSource<object> completedTask = new TaskCompletionSource<object>();
StatusReport[id] = new Answare(completedTask)
{
HasAnswared = true,
Value = result
};
return completedTask.Task;
}
}
After that the question implementation
public interface IQuestionBox
{
string Id { get; }
Task<bool> ShowYesNoQuestionBox(string question);
HtmlString ShowMessage();
}
class QuestionBox : IQuestionBox
{
Process CurrentProcess { get; set; }
public string Id { get; } = Guid.NewGuid().ToString();
private string Question { get; set; }
public QuestionBox(Process currentProcess)
{
CurrentProcess = currentProcess;
CurrentProcess.RegisterForAnswer(this.Id);
}
public Task<bool> ShowYesNoQuestionBox(string question)
{
Question = question;
CurrentProcess.Release();
return AwaitForAnswer();
}
public HtmlString ShowMessage()
{
HtmlString htm = new HtmlString(
$"<script>showMessage('{Question}', '{Id}');</script>"
);
return htm;
}
private Task<bool> AwaitForAnswer()
{
TaskCompletionSource<bool> awaitableResult = new TaskCompletionSource<bool>(true);
Task.Factory.StartNew(() =>
{
while (true)
{
Thread.Sleep(2000);
var answare = CurrentProcess.GetAnswer(this.Id);
if (!answare.HasAnswered)
continue;
awaitableResult.SetResult(answare.Value);
break;
}
});
return awaitableResult.Task;
}
}
The differences for yours implementaion are:
1 - I create an Identifier to know for who I have to send the aswer, or just to stop the process.
2 - I receive a Process as parameter, because this allows us to call the method
CurrentProcess.Release(); in ShowYesNoQuestion, here in specific, releases the process to send the response responsable to interact with the user.
3 - I create the method AwaitForAnswer, here one more time we use from the TaskCompletionSource class. As you can see in this method we have a loop, this loop is responsable to wait for the user interaction, and til receive a response it doesn't release the process.
4 - I create the method ShowMessage that create a simple html script alert to simulate the user interaction.
Then a simple process class as you should be in your bussiness logical:
public class SaleService
{
public async Task<string> GetValue(IQuestionBox qbox)
{
if (await qbox.ShowYesNoQuestionBox("Do you think Edney is the big guy ?"))
{
return "I knew, Edney is the big guy";
}
return "No I disagree";
}
}
And then the class to represent the user answer
public class Answer
{
// just a sugar to represent empty responses
public static Answer Empty { get; } = new Answer { Value = true, HasAnswered = true };
public Answer()
{
}
// one more time abusing from TaskCompletionSource<object>, because with this guy we are abble to send the result from the process to the user
public Answer(TaskCompletionSource<object> completedTask)
{
CompletedTask = completedTask;
}
private TaskCompletionSource<object> CompletedTask { get; set; }
public bool Value { get; set; }
public bool HasAnswered { get; set; }
// this method as you can see, will set the result and release the task for the user
public void UserResponse(object response)
{
CompletedTask.SetResult(response);
}
}
Now we use all the entire structure create for this:
[HttpPost]
public IActionResult Index(string parametro)
{
// create your process an run it, passing what you want to do
Process process = new Process();
var question = process.Run(async (questionBox) =>
{
// we start the service
SaleService service = new SaleService();
// wait for the result
var result = await service.GetValue(questionBox);
// and close the process with the result from the process
process.End(result);
});
return View(question);
}
// here we have the method that deliver us the user response interaction
[HttpPost]
public async Task<JsonResult> Answer(bool result, string id)
{
// we define the result for an Id on the process
var response = await Process.DefineAnswer(id, result);
// get the response from process.End used bellow
// and return to the user
return Json(response);
}
and in your view
<!-- Use the question as the model page -->
#model InjetandoInteracaoComUsuario.Controllers.IQuestionBox
<form asp-controller="Home" asp-action="Index">
<!-- create a simple form with a simple button to submit the home -->
<input type="submit" name="btnDoSomething" value="All about Edney" />
</form>
<!-- in the scripts section we create the function that we call on the method ShowMessage, remember?-->
<!-- this method request the action answer passing the questionbox id, and the result from a simple confirm -->
<!-- And to finalize, it just show an alert with the process result -->
#section scripts{
<script>
function showMessage(message, id) {
var confirm = window.confirm(message);
$.post("/Home/Answer", { result: confirm, id: id }, function (e) {
alert(e);
})
}
</script>
#Model?.ShowMessage()
}
As I've said, I realy disagree with this pratices, the correct should to write a new dll, to support the web enviroment, but I hope it help you.
I put the project on github to you can download an understand all the solution
I realy hope it can help you
You can create a web socket connection from client side to server side. And work with front-end content with web socket request. It could be implemented as following:
Client side:
$app = {
uiEventsSocket : null,
initUIEventsConnection : function(url) {
//create a web socket connection
if (typeof (WebSocket) !== 'undefined') {
this.uiEventsSocket = new WebSocket(url);
} else if (typeof (MozWebSocket) !== 'undefined') {
this.uiEventsSocket = new MozWebSocket(url);
} else {
console.error('WebSockets unavailable.');
}
//notify if there is an web socket error
this.uiEventsSocket.onerror = function () {
console.error('WebSocket raised error.');
}
this.uiEventsSocket.onopen = function () {
console.log("Connection to " + url + " established");
}
//handling message from server side
this.uiEventsSocket.onmessage = function (msg) {
this._handleMessage(msg.data);
};
},
_handleMessage : function(data){
//the message should be in json format
//the next line fails if it is not
var command = JSON.parse(data);
//here is handling the request to show prompt
if (command.CommandType == 'yesNo') {
var message = command.Message;
var result = confirm(message);
//not sure that bool value will be successfully converted
this.uiEventsSocket.send(result ? "true" : "false");
}
}
}
And init it from ready or load event:
window.onload = function() { $app.initUIEventsConnection(yourUrl); }
Note that you url should begin with ws:// instead of http:// and wss:// instead of https:// (Web Sockets and Web Sockets Secure).
Server side.
Here is a good article for how to setup web sockets at asp.net core application or you could find another one. Note that you should group web socket connections from single user and if you want to send a message to the concrete user, you should send message for every connection from this user.
Every web socket you should accept with AcceptWebSocketAsync() method call and then add instance of this web socket to singleton, which contains a set of web sockets connection groupped by user.
The following class will be used to operate commands:
public class UICommand
{
public string CommandType { get; set; }
public string Message { get; set; }
public Type ReturnType { get; set; }
}
And a full code of singleton for handling sockets
public class WebSocketsSingleton
{
private static WebSocketsSingleton _instance = null;
//here stored web sockets groupped by user
//you could use user Id or another marker to exactly determine the user
private Dictionary<string, List<WebSocket>> _connectedSockets;
//for a thread-safety usage
private static readonly ReaderWriterLockSlim Locker = new ReaderWriterLockSlim();
public static WebSocketsSingleton Instance {
get {
if (this._instance == null)
{
this._instance = new WebSocketsSingleton();
}
return this._instance;
}
}
private WebSocketsSingleton()
{
this._connectedSockets = new Dictionary<string, List<WebSocket>>();
}
/// <summary>
/// Adds a socket into the required collection
/// </summary>
public void AddSocket(string userName, WebSocket ws)
{
if (!this._connectedSockets.ContainsKey(userName))
{
Locker.EnterWriteLock();
try
{
this._connectedSockets.Add(userName, new List<WebSocket>());
}
finally
{
Locker.ExitWriteLock();
}
}
Locker.EnterWriteLock();
try
{
this._connectedSockets[userName].Add(ws);
}
finally
{
Locker.ExitWriteLock();
}
}
/// <summary>
/// Sends a UI command to required user
/// </summary>
public async Task<string> SendAsync(string userName, UICommand command)
{
if (this._connectedSockets.ContainsKey(userName))
{
var sendData = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(command));
foreach(var item in this._connectedSockets[userName])
{
try
{
await item.SendAsync(new ArraySegment<byte>(sendData), WebSocketMessageType.Text, true, CancellationToken.None);
}
catch (ObjectDisposedException)
{
//socket removed from front end side
}
}
var buffer = new ArraySegment<byte>(new byte[1024]);
var token = CancellationToken.None;
foreach(var item in this._connectedSockets[userName])
{
await Task.Run(async () => {
var tempResult = await item.ReceiveAsync(buffer, token);
//result received
token = new CancellationToken(true);
});
}
var resultStr = Encoding.Utf8.GetString(buffer.Array);
if (command.ReturnType == typeof(bool))
{
return resultStr.ToLower() == "true";
}
//other methods to convert result into required type
return resultStr;
}
return null;
}
}
Explanation:
on establishing connection from web socket it will be added with
AddSocket method
on sending request to show a message, the required command will be passed into SendAsync method
the command will be serialized to JSON (using Json.Net, however you could serialize in your way) and send to all sockets, related to the required user
after the command sent, application will wait for respond from front end side
the result will be converted to required type and sent back to your IQuestionBox
In the web socket handling your should add some kind of the following code:
app.Use(async (http, next) =>
{
if (http.WebSockets.IsWebSocketRequest)
{
var webSocket = await http.WebSockets.AcceptWebSocketAsync();
var userName = HttpContext.Current.User.Identity.Name;
WebSocketsSingleton.Instance.AddSocket(userName, webSocket);
while(webSocket.State == WebSocketState.Open)
{
//waiting till it is not closed
}
//removing this web socket from the collection
}
});
And your method implementation of ShowYesNoQuestionBox should be kind of following:
public async Task<bool> ShowYesNoQuestionBox(string userName, string text)
{
var command = new UICommand
{
CommandType = "yesNo",
Message = text,
ReturnType = typeof(bool)
};
return await WebSocketsSingleton.Instance.SendAsync(string userName, command);
}
Note that there should be added userName to prevent sending the same message to all of the connected users.
WebSocket should create the persistent connection between server and client sides, so you could simply send commands in two ways.
I am kindly new to Asp.Net Core, so the final implementation could be a bit different from this.
It's actually much the same, except your UI is sort of disconnected and proxied with the HTTP protocol for the most part.
you essentially need to build the same code as your WPF code but then in the browser construct ajax calls in to the controller actions to apply your logic.
To clarify ...
so lets say you are building up a process over a series of questions that based on the users answer you put different steps in to the process.
You can either ...
build the process in the database
build it in session on the server
build it on the client as a js object
then do a post for execution ofthe constructed process.
think of the "statelessness" as a series of short interactions, but the state you keep between them can be done either on the client, in a db or in the users logged in session on the web server.
In your controller you can add an ActionResult that will give you the html response to your jquery modal popup request. Here is an example
public class MController : Controller {
public ActionResult doWork(requirement IQuestionBox)
{
// model is already modelBound/IOC resolved
return PartialView("_doWork", requirement );
}
}
//scripts
$(function(){
$.ajax({
url:"/m/doWork",
type:"get",
success:function(data){
$modal.html(data); // bind to modal
}
});
});
Apologies for not fully understanding the question.
hope this helps!
I've just started to play around with WebSockets and ASP.NET and have run into a weird issue. I'm building a very primitive ASP.NET 4.5 WebAPI application that is supposed to function as an echo-server like so:
using Microsoft.Web.WebSockets;
// ...
namespace MyControllers
{
internal class EchoHandler : WebSocketHandler
{
public override void OnClose()
{
System.Diagnostics.Debug.Write("Close");
}
public override void OnError()
{
System.Diagnostics.Debug.Write("Error: " + this.Error.ToString());
}
public override void OnOpen()
{
System.Diagnostics.Debug.Write("Open");
}
public override void OnMessage(string message)
{
System.Diagnostics.Debug.Write("Message: " + message);
this.Send("Echo: " + message);
}
}
public class EchoController : ApiController
{
public HttpResponseMessage Get()
{
if (HttpContext.Current.IsWebSocketRequest)
{
HttpContext.Current.AcceptWebSocketRequest(new EchoHandler());
return Request.CreateResponse(HttpStatusCode.SwitchingProtocols);
}
else
{
return Request.CreateResponse(HttpStatusCode.BadRequest);
}
}
}
}
I'm connecting to this service using a Windows Store Application written in C#. The relevant code looks like this:
class WebsocketTest
{
private MessageWebSocket webSocket;
private DataWriter messageWriter;
private async Task Connect()
{
var server = new Uri("ws://127.0.0.1:81/");
webSocket = new MessageWebSocket();
webSocket.Control.MessageType = SocketMessageType.Utf8;
webSocket.MessageReceived += messageWebSocket_MessageReceived;
webSocket.Closed += messageWebSocket_Closed;
await webSocket.ConnectAsync(server);
messageWebSocket = webSocket;
messageWriter = new DataWriter(webSocket.OutputStream);
}
private async Task Send(string message)
{
try
{
messageWriter.WriteString(message);
await messageWriter.StoreAsync();
}
catch (Exception ex)
{
var error = WebSocketError.GetStatus(ex.GetBaseException().HResult);
}
}
}
This works well for a while, but after an arbitrary number of messages have been sent back and forth, OnError() is invoked on the server and I get the following exception: "The I/O operation has been aborted because of either a thread exit or an application request" (It's the "this.Send(...)" that seems to be causing it). If I keep sending stuff on the client, I get a "ConnectionAborted" error when calling "dataWriter.StoreAsync()".
The error occurs every time, but it takes a varying number of messages before it does. Using longer messages seems to speed up the process.
For testing, I also tried using plain AspNetWebSockets instead of a WebSocketHandler but with the same outcome.
Any ideas?
Thanks a ton in advance,
Kai
Its a bug (reported by me):
https://connect.microsoft.com/VisualStudio/feedbackdetail/view/976851/server-websocket-closed-abruptly-the-i-o-operation-has-been-aborted-because-of-either-a-thread-exit-or-an-application-request
I have been trying to find a workaround for quite some time without being successful. I'm using the HttpListener but the symptom is the same. Now I have changed implementation to a third party library and the problem seems to have been resolved.
I am using latest SignalR (v:1.1.1), and trying to simple call the Hub method periodically, every 3 seconds. I have seen many questions here and have duplicated the way, but GetHubContext method doesn't seem to be returning the correct instance of the class, so I can't call the methods of that class. You can duplicate the case with the following steps:
MyHub.cs:
public class MyHub : Hub
{
public void SendMessage(string message)
{
Clients.All.triggerMessage(message);
}
}
Global.asax:
Task.Factory.StartNew(() =>
{
while (true)
{
var myHub = GlobalHost.ConnectionManager.GetHubContext<MyHub>();
myHub.Clients.All.SendMessage("Hello World");
System.Threading.Thread.Sleep(3000);
}
})
.ContinueWith(t => { throw new Exception("The task threw an exception", t.Exception); }, TaskContinuationOptions.OnlyOnFaulted);
I think this is as simple as it gets. I think this is correct way of doing it, but the debugger never hits SendMessage method. Does anyone know am I missing something very obvious? I am just trying to schedule a call to the SignalR client from the server for every 3 seconds.
On your Global.asax file, when you call 'myHub.Clients.All.SendMessage("Hello World")' it sends a message to the client, it does not call the SendMessage method in your class MyHub.
Please read SignalR Documentation to see some samples
I ended changing the way the hub was created:
MyHostHub.cs
private readonly MyHost _host;
public MyHostHub(){ _host = new MyHost(); }
MyHost:
private readonly static Lazy<IHubConnectionContext> _clients = new Lazy<IHubConnectionContext>(() => GlobalHost.ConnectionManager.GetHubContext<MyHostHub>().Clients);
private IHubConnectionContext Clients
{
get { return _clients.Value; }
}
public void SendMessage(string message)
{
Clients.All.triggerMessage(message);
}
My Global.asax:
Task.Factory.StartNew(() =>
{
while (true)
{
var myHost = ObjectFactory.GetInstance<MyHost>();
myHost.SendMessage();
Thread.Sleep(3000);
}
})
.ContinueWith(t => { throw new Exception("The task threw an exception", t.Exception); }, TaskContinuationOptions.OnlyOnFaulted);
This seems to be working just fine. Basically I moved out the code from the Hub class to another class that I can call in Global.asax but my hub has a reference for host.