What is the timing for when the SignalR connection is terminated from the browser?

Question

What is the timing for when the SignalR connection is terminated from the browser?

Currently, I am developing a chat application using SignalR 2.0, like many others in the same field.

In my Win8.1 application, when the user closes the application, the hub receives the OnDisconnected event and removes the user from the list on the hub. A message is then sent to all clients informing them that the user has left the chat.

However, when I integrate SignalR and JavaScript into a webpage, the hub does not receive any notification when the tab or browser is closed...

Does anyone have any idea how to properly close the connection?

This is what I have coded:

Startup Hub

[assembly: OwinStartup(typeof(ChatServer.Startup))]

namespace ChatServer
{
public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        // Map all hubs to "/signalr"
        app.MapSignalR();
    }
}
}

Hub

[HubName("ChatHub")]
public class ChatHub : Hub
{
    private static List<User> Users = new List<User>();
    
    // Rest of the code remains unchanged...

HTML - Javascript:

Javascript:

// The JavaScript section goes here...

Win8.1 client

// The Win8.1 client part also remains the same...

Even after following these steps, my hub fails to trigger the OnDisconnected event when closing the tab, browser, or navigating to another site. This issue persists despite using Chrome Version 32.0.1700.68 beta-m or Internet Explorer 11 as browsers.

javascript signalr

Answer 1

Answer №1

Are you wondering how to determine if a specific user has left or closed the browser? You can achieve this by sending notifications to other users when a user enters or exits.

The issue may be related to not handling OnConnected and OnDisconnected events correctly. To resolve this, it's important to understand that each client connecting to a hub is assigned a unique connection ID, which can be accessed through the Context.ConnectionId property of the hub context. Clients trigger OnConnected when they join, and OnDisconnected when they leave. Below is an example implementation:

Hub Class

[HubName("ChatHub")]
public class ChatHub : Hub
{
    private static List<User> Users = new List<User>();
    
    public void Send(string message)
    {
        var name = Context.User.Identity.Name;
        Clients.All.broadcastMessage(name, message, DateTime.Now.ToShortDateString());
    }

    public override Task OnConnected()
    {
        User user = new User() { Name = Context.User.Identity.Name, ConnectionID = Context.ConnectionId };
        Users.Add(user);
        Clients.Others.userConnected(user.Name);
        return base.OnConnected();
    }

    public override Task OnDisconnected()
    {
        if (Users.Any(x => x.ConnectionID == Context.ConnectionId))
        {
            User user = Users.First(x => x.ConnectionID == Context.ConnectionId);
            Clients.Others.userLeft(user.Name);   
            Users.Remove(user);
        }
        return base.OnDisconnected();
    }
}

View

<input type="text" id="message" />
<button class="btn">Send</button>
<ul id="contents"></ul>

@section scripts
{
    <script src="~/Scripts/jquery-1.10.2.js"></script>
    <script src="~/Scripts/jquery.signalR-2.0.1.js"></script>
    <script src="/signalr/hubs"></script>

    <script>

        var chatHub = $.connection.ChatHub;
        chatHub.client.broadcastMessage = function (name, message, time) {
            var encodedName = $('<div />').text(name).html();
            var encodedMsg = $('<div />').text(message).html();
            var encodedTime = $('<div />').text(time).html();
            $('#contents').append('<li><strong>' + encodedName + '</strong>:&nbsp;&nbsp;' + encodedMsg + '</strong>:&nbsp;&nbsp;' + encodedTime + '</li>');
        };

        chatHub.client.userConnected = function (data) {          
            $('#contents').append('<li>Welcome<strong>' + '</strong>:' + data + '</li>');
        };

        chatHub.client.userLeft = function (data) {
            $('#contents').append('<li>Goodbye<strong>' + '</strong>:' + data + '</li>');
        };

        $(".btn").on("click", function() {
            chatHub.server.send($("#message").val());
        });

        $.connection.hub.start().done(function() {
            console.log("Connected...");
        });
    </script>
}

Answer 2

Are you wondering how to determine if a specific user has left or closed the browser? You can achieve this by sending notifications to other users when a user enters or exits.

The issue may be related to not handling OnConnected and OnDisconnected events correctly. To resolve this, it's important to understand that each client connecting to a hub is assigned a unique connection ID, which can be accessed through the Context.ConnectionId property of the hub context. Clients trigger OnConnected when they join, and OnDisconnected when they leave. Below is an example implementation:

Hub Class

[HubName("ChatHub")]
public class ChatHub : Hub
{
    private static List<User> Users = new List<User>();
    
    public void Send(string message)
    {
        var name = Context.User.Identity.Name;
        Clients.All.broadcastMessage(name, message, DateTime.Now.ToShortDateString());
    }

    public override Task OnConnected()
    {
        User user = new User() { Name = Context.User.Identity.Name, ConnectionID = Context.ConnectionId };
        Users.Add(user);
        Clients.Others.userConnected(user.Name);
        return base.OnConnected();
    }

    public override Task OnDisconnected()
    {
        if (Users.Any(x => x.ConnectionID == Context.ConnectionId))
        {
            User user = Users.First(x => x.ConnectionID == Context.ConnectionId);
            Clients.Others.userLeft(user.Name);   
            Users.Remove(user);
        }
        return base.OnDisconnected();
    }
}

View

<input type="text" id="message" />
<button class="btn">Send</button>
<ul id="contents"></ul>

@section scripts
{
    <script src="~/Scripts/jquery-1.10.2.js"></script>
    <script src="~/Scripts/jquery.signalR-2.0.1.js"></script>
    <script src="/signalr/hubs"></script>

    <script>

        var chatHub = $.connection.ChatHub;
        chatHub.client.broadcastMessage = function (name, message, time) {
            var encodedName = $('<div />').text(name).html();
            var encodedMsg = $('<div />').text(message).html();
            var encodedTime = $('<div />').text(time).html();
            $('#contents').append('<li><strong>' + encodedName + '</strong>:&nbsp;&nbsp;' + encodedMsg + '</strong>:&nbsp;&nbsp;' + encodedTime + '</li>');
        };

        chatHub.client.userConnected = function (data) {          
            $('#contents').append('<li>Welcome<strong>' + '</strong>:' + data + '</li>');
        };

        chatHub.client.userLeft = function (data) {
            $('#contents').append('<li>Goodbye<strong>' + '</strong>:' + data + '</li>');
        };

        $(".btn").on("click", function() {
            chatHub.server.send($("#message").val());
        });

        $.connection.hub.start().done(function() {
            console.log("Connected...");
        });
    </script>
}

Answer 3

Answer №2

It seems like you may be encountering a problem similar to the one discussed here: https://github.com/SignalR/SignalR/issues/2719

In short, there is a known issue in Chrome 31 that has been resolved in Chrome Canary, causing SignalR to not immediately trigger OnDisconnected.

If this is the case, you can implement the workaround I proposed in the discussion by adding the following code snippet to your JavaScript:

window.onbeforeunload = function (e) {
    $.connection.hub.stop();
};

Even with this bug and without the workaround, SignalR should still trigger OnDisconnected after approximately 35 seconds when the web browser closes the page where SignalR is hosted.

Could you please provide more information on which browsers you are facing this issue with and under what circumstances? For example, closing the tab, closing the window, refreshing the page, navigating to another page on the same site, or navigating to a different website, etc.

Answer 4

It seems like you may be encountering a problem similar to the one discussed here: https://github.com/SignalR/SignalR/issues/2719

In short, there is a known issue in Chrome 31 that has been resolved in Chrome Canary, causing SignalR to not immediately trigger OnDisconnected.

If this is the case, you can implement the workaround I proposed in the discussion by adding the following code snippet to your JavaScript:

window.onbeforeunload = function (e) {
    $.connection.hub.stop();
};

Even with this bug and without the workaround, SignalR should still trigger OnDisconnected after approximately 35 seconds when the web browser closes the page where SignalR is hosted.

Could you please provide more information on which browsers you are facing this issue with and under what circumstances? For example, closing the tab, closing the window, refreshing the page, navigating to another page on the same site, or navigating to a different website, etc.

What is the timing for when the SignalR connection is terminated from the browser?

Answer №1

Answer №2

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