Get names of Online users connected to a Server - asp.net

I am new to asp.net. I have gone through this link which has shown how to count the online users connected to a server using asp.net. (which is working when I tried)
My question is: What should I change in that code (Global.asax) so that It shows all the names of the connected users instead of counting them.
I created a chat application which stores the name of the connected user in a variable chatUsername in js file as shown below:
js file
var chatUsername = window.prompt("Enter Username:", "");
//
chat.client.addMessage = //Function
//
chat.server.send(chatUsername);
.aspx.cs file
//Using SignalR (I think this doesnt matter)
public class Chat : Hub
{
public void Send(string from)
{
// Call the addMessage method on all clients
Clients.All.addMessage(from);
}
}
You can find my complete code here
EDIT: Please provide a simple example related only to asp.net or signalr (no other technologies like MVC)
Please help.

Edit: following code refers to SignalR v0.5, not the latest 1.0Alpha2, but I believe the reasoning is the same
To do this you need to add several steps to your SignalR connection process, both in the server and in the client:
on the server side:
on application start-up, for example, you can instantiate a static in-memory repository (can be a dictionary of ) that will serve as the user repository to store all currently connected users.
In the hub you need to handle the Disconnect event (when a user disconnects, needs to be removed from the user repository as well) and notify all other clients that this user disconnected
In the hub you need to add two new methods (the names can be whatever you want) that will help client connect to the system and get the list of currently connected users:
GetConnectedUsers() that just returns a collection of connected users
Joined() where the Hub will create a new User, using the info stored in the round-trip state (the username selected by the client) and the SignalR connection ID, and add the newly created user to the in-memory repository.
on the client side:
First you need to instantiate the javascript object that relates to your server-side hub
var chat = $.connection.chat;
chat.username = chatUsername;
Then implements all the functions that will be called by the hub and finally connect to the hub:
// Step 1: Start the connection
// Step 2: Get all currenlty connected users
// Step 3: Join to the chat and notify all the clients (me included) that there is a new user connected
$.connection.hub.start()
.done(function () {
chat.getConnectedUsers()
.done(/*display your contacts*/);
});
}).done(function () {
chat.joined();
});
});
});
If you are asking why we need to add a stage like "chat.joined()" is because in the method on the Hub that is handling the connection event, the round-trip state is not yet available, so the hub cannot retrieve the username chosen by the user.
Anyway I made a blog post to show more in detail how to create a basic SignalR chat web application using Asp.Net MVC, and it is available at:
http://thewayofcode.wordpress.com/2012/07/24/chatr-just-another-chat-application-using-signalr/
In the post you will also find a link to the github repository where the source is published.
I hope this helps.
Valerio

Apparently, you are using Signal-R - so try tracking state of online users (i.e. connected clients) in java-script itself. Use Connected/Disconnected/Reconnected server side events to broadcast to all clients - from documentation:
public class Chat : Hub
{
public override Task OnConnected()
{
return Clients.All.joined(Context.ConnectionId, DateTime.Now.ToString());
}
public override Task OnDisconnected()
{
return Clients.All.leave(Context.ConnectionId, DateTime.Now.ToString());
}
public override Task OnReconnected()
{
return Clients.All.rejoined(Context.ConnectionId, DateTime.Now.ToString());
}
}
A global server side store (for example - a static dictionary) can be used to store state against the connection id - that way, this dictionary can give you users for needed connection ids. For example,
// dis-claimer: untested code - just to give the idea/hint/outline
public class Chat : Hub
{
// change to use Concurrent Dictionary (or do thread-safe access)
static Dictionary<string, User> _users = new Dictionary<string, User>()
// call from client when it goes online
public void Join(string name)
{
var connId = this.Context.ConnectionId;
__users.Add(connId, new User(connId, name));
}
public override Task OnConnected()
{
return Clients.All.joined(_users[Context.ConnectionId], DateTime.Now.ToString());
}
public override Task OnDisconnected()
{
var user = _users[Context.ConnectionId];
_users.Remove(Context.ConnectionId);
return Clients.All.leave(user, DateTime.Now.ToString());
}
public List<User> GetUsers()
{
return _users.Values.ToList()
}
}

I think this should work for you :-
void Application_Start(object sender, EventArgs e)
{
// Code that runs on application startup
Application["OnlineUsers"] = 0;
List<string> list = new List<string>();
}
//First check if it is Authenticated request:-
void Session_Start(object sender, EventArgs e)
{
if(Request.IsAuthenticated)
list.Add(User.Identity.Name);
//your rest of code .......
}
list will return you all the username who are online :-

Related

signlar hub method termination

I'd like to know if an Hub method called from js client is
executed completely also if client disconnected during execution
For example..
public virtual void Join(int userId)
{
using (var context = new HubConnectionContext(this, RoomId, userId))
{
T workflow = GetWorkflow(context);
workflow.OnUserJoin();
}
}
I can be sure that the Dispose Method of HubConnectionContext is called also if client disconnect during using block?

SignalR - access clients from server-side business logic

I have a requirement to start a process on the server that may run for several minutes, so I was thinking of exposing the following hub method:-
public async Task Start()
{
await Task.Run(() => _myService.Start());
}
There would also be a Stop() method that allows a client to stop the running process, probably via a cancellation token. I've also omitted code that prevents it from being started if already running, error handling, etc.
Additionally, the long-running process will be collecting data which it needs to periodically broadcast back to the client(s), so I was wondering about using an event - something like this:-
public async Task Start()
{
_myService.AfterDataCollected += AfterDataCollectedHandler;
await Task.Run(() => _myService.Start());
_myService.AfterDataCollected -= AfterDataCollectedHandler;
}
private void AfterDataCollectedHandler(object sender, MyDataEventArgs e)
{
Clients.All.SendData(e.Data);
}
Is this an acceptable solution or is there a "better" way?
You don't need to use SignalR to start the work, you can use the applications already existing framework / design / API for this and only use SignalR for the pub sub part.
I did this for my current customers project, a user starts a work and all tabs belonging to that user is updated using signalr, I used a out sun library called SignalR.EventAggregatorProxy to abstract the domain from SignalR. Disclaimer : I'm the author of said library
http://andersmalmgren.com/2014/05/27/client-server-event-aggregation-with-signalr/
edit: Using the .NET client your code would look something like this
public class MyViewModel : IHandle<WorkProgress>
{
public MyViewModel(IEventAggregator eventAggregator)
{
eventAggregator.Subscribe(this);
}
public void Handle(WorkProgress message)
{
//Act on work progress
}
}

Using SignalR to send Real Time Notification

I want to create a new system to send real time trade execution messages to users using SignalR. In the old system, each client connects to the trading server using Java Applet TCP connection.
I use the following tutorial as reference
http://www.asp.net/signalr/overview/getting-started/tutorial-server-broadcast-with-signalr
There is a line of code in the StockTicker constructor to update the stock prices:
_timer = new Timer(UpdateStockPrices, null, _updateInterval, _updateInterval);
However, I need to update trade execution in real time instead of updating stock prices per 250ms.
Is it okay to create TCP connection to my trading server per client in the constructor? It seems that in the sample code, the constructor of StockTicker (i.e. my TradingManager) will be called one time only. But in my design, I want to create a TCP connection per client. How should I change the code to do this?
Here is my code:
TradingHub.cs
public class TradingHub : Hub
{
private readonly TradingManager _tradingManager;
public TradingHub() : this(TradingManager.Instance) { }
public TradingHub(TradingManager tradingManager)
{
_tradingManager = tradingManager;
}
...
}
TradingManager.cs
public class TradingManager
{
// Singleton instance
private readonly static Lazy<TradingManager> _instance = new Lazy<TradingManager>(
() => new TradingManager());
...
public static TradingManager Instance{ get{ return _instance.Value; } }
public TradingManager()
{
...
this.apiConnector.MessageReceived += new CustomEventHandler(this.api_MessageReceived);
init();
}
private IHubConnectionContext<dynamic> Clients { get; set; }
private void init()
{
TradingSession tradingSession = getLoginSession(user);
// connect to trading server using TCP connection
this.apiConnector.ensureConnected(host, port, tradingSession);
// send keep alive message to trading server periodically
_timer = new Timer(sendKeepAlive, null, _updateInterval, _updateInterval);
}
private void api_MessageReceived(object sender, CustomEventArgs e)
{
// when web server receives trade execution from server, send out the message immediately
Clients.Caller.SendTradeExecutionMessage(......);
}
public static TradingSession getLoginSession(string user)
{
...
}
private void sendKeepAlive(object state)
{
...
}
}
If you were to make a new TradingManager in your Hub constructor instead of referencing a singleton, you would be creating more than one TradingManager per SignalR connection. Hubs are reinstantiated per method call. Every time you invoke a hub method or a hub event is called (e.g. OnConnected, OnReconnected, OnDisconnected), your constructor will be called.
However, OnConnected is only called once per SignalR connection. By the way, SignalR connections are completely orthogonal to TCP connections. With the long polling transport, for example, a new HTTP request is sent each time a message is received.
I think you want to create a new TradingManager instance each time OnConnected is called and potentially associate it with the client's Context.ConnectionId and store it (perhaps in a ConcurrentDictionary) so you can retrieve it using the connection id when your Hub methods are called. You can then dereference the stored TradingManager instance for a given connection id in OnDisconnected.
You can learn more about SignalR connections at:
http://www.asp.net/signalr/overview/guide-to-the-api/handling-connection-lifetime-events
You can learn more about the Hub API and the On* methods at:
http://www.asp.net/signalr/overview/guide-to-the-api/hubs-api-guide-server#connectionlifetime

ASP.net how to long polling with PokeIn?

I want to make a service that notify the user in case there are some new messages sent to him. Thus I want to use some Comet framework that provide the server push ability. So I have looked into PokeIn.
Just wondering a thing. I have checked on the samples that they have on the website. None of them look into the database to retrieve new entries if there are some. But it is just a matter of modification to it I guess.
One of the sample implement this long polling by using a sleep on the server side. So if I use the same approach I can check the database, if there are any new entries, every 5 seconds. However this approach doesn't seem to be much different from when using polling on the client side with javascript.
This part is from a sample. As can be seen they put a sleep there for to update current time for everybody.
static void UpdateClients()
{
while (true)
{
//.. code to check database
if (CometWorker.ActiveClientCount > 0)
{
CometWorker.SendToAll(JSON.Method("UpdateTime", DateTime.Now));
}
Thread.Sleep(500);
}
}
So I wonder is this how I should implement the message notifier? It seems that the above approach is still going to push a huge load demand on the server side. The message notifier is intend to work same way as the one found Facebook.
You shouldn't implement this way, that sample is only implemented like that because the keep PokeIn related part is clear. You should implement SQL part as mentioned http://www.codeproject.com/Articles/12335/Using-SqlDependency-for-data-change-events
in order to track changes on database.
So, when you have something to send, call one of the PokeIn methods for the client side delivery. I don't know, how much your application is time critical because in addition to reverse ajax, PokeIn's internal websocket feature is very easy to activate and delivers messages to client quite fast.
You can do this with database as #Zuuum said, but I implemented it in a different way.
I'm using ASP.NET MVC with PokeIn and EF in a Windows Azure environment:
I have domain events similar to this approach: Strengthening your domain: Domain Events
When someone invokes an action, that's a Unit of Work
If that UOW succeeds then I raise a domain event (e.g. ChatMessageSent)
I have subscribers for these domain events so they can receive the event and forward the message to the PokeIn listeners
I use this pattern for all my real-time needs on my game site (making moves, actions etc in a game), I don't want to advertise it here, you can find it through me if you want.
I always use this pattern as a duplex communication solution so everybody gets their update via PokeIn, even the user who invoked the action so every client will behave the same. So when someone calls an action it won't return anything except the success signal.
The next examples are won't work because they are only snippets to demonstrate the flow
Here is an action snippet from my code:
[HttpPost]
[UnitOfWork]
[RestrictToAjax]
[ValidateAntiForgeryToken]
public JsonResult Post(SendMessageViewModel msg)
{
if (ModelState.IsValid)
{
var chatMessage = new ChatMessage
{
ContainerType = msg.ContainerType,
ContainerID = msg.ContainerID,
Message = _xssEncoder.Encode(msg.Message),
User = _profileService.CurrentUser
};
_chatRepository.AddMessage(chatMessage);
OnSuccessfulUoW = () => EventBroker.Current.Send(this, new ChatMessageSentPayload(chatMessage));
}
return Json(Constants.AjaxOk);
}
And the (simplified) EventBroker implementation:
public class UnityEventBroker : EventBroker
{
private readonly IUnityContainer _container;
public UnityEventBroker(IUnityContainer container)
{
_container = container;
}
public override void Send<TPayload>(object sender, TPayload payload)
{
var subscribers = _container.ResolveAll<IEventSubscriber<TPayload>>();
if (subscribers == null) return;
foreach (var subscriber in subscribers)
{
subscriber.Receive(sender, payload);
}
}
}
And the even more simplified subscriber:
public class ChatMessageSentSubscriber : IEventSubscriber<ChatMessageSentPayload>
{
public void Receive(object sender, ChatMessageSentPayload payload)
{
var message = payload.Message;
var content = SiteContent.Global;
var clients = Client.GetClients(c => c.ContentID == message.ContainerID && c.Content == content)
.Select(c => c.ClientID)
.ToArray();
var dto = ObjectMapper.Current.Map<ChatMessage, ChatMessageSentDto>(message);
var json = PokeIn.JSON.Method("pokein", dto);
CometWorker.SendToClients(clients, json);
}
}

how can I send a message with signalr to the client?

I want to use signalR for my clint browser website so it can receive messages from the server when a new order is added. So I want it to react to a server side event that is not triggered by any browser.
There are multiple users on the website. A user should be notified when there is a new order placed for him on he server. How an I notify only a specific user, and do this from the method that adds the user?
Is there any code like:
var chat=new Chat();
chat.Send("hihi");
placed in AddOrder method, with
public class Chat : Hub
{
public void Send(string message)
{
// Call the addMessage method on all clients
Clients.refresh(message);
}
}
You can override the default client id (used to identify the users browser window) and replace with your own. Your client id would come from your membership provider.
Create a new class and implement IConnectionIdGenerator.
public class UserIdClientIdFactory : IConnectionIdGenerator
{
public string GenerateConnectionId(IRequest request)
{
return Guid.NewGuid().ToString();
}
}
The method above just creates a new Guid, but you would return the customers id from your membership provider.
You then need to register this new class with SignalR dependencyresolver, so in the Application_Start method in the global.asax file add the following line
GlobalHost.DependencyResolver.Register(typeof(IConnectionIdGenerator),
() => new UserIdClientIdFactory());
When a new order is placed you would then get the specific client and broadcast a message to them, for example:
//clientId matches the user id from you membership provider.
var clients = GlobalHost.ConnectionManager.GetHubContext().Clients;
clients[clientId].yourClientSideCallBackMethodGoesHere(someValue);
You have to store the Context.ConnectionId for all connected users, tie that to your website users and then use Clients[connectionId].addMessage(data);
One way you can do this is to hold a collection of Users (website users) each paired to a connection Id. You can then use SignalR events OnConnected / OnDisconnected to pop users in and out of this list.
E.g.
public override Task OnConnected()
{
// Add users here with Context.ConnectionId
}
public override Task OnDisconnected()
{
// Remove users from collection here by identifying them with Context.ConnectionId
}

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