How to determine server disconnection from SignalR client?

Question

How can a SignalR JavaScript client detect when a connection with the server is lost?

Answer 1

A hub has a method disconnect which will allow you to add a callback when disconnection takes place:

myHub.disconnect(function() {
  alert('Server has disconnected');
});

If you aren't using hubs then the code for the disconnect method will help you out:

$(connection).bind("onDisconnect", function (e, data) {
  callback.call(connection);
});

This shows the syntax for hooking onto the onDisconnect event of the underlying connection.

Answer 2

This worked for me using "@aspnet/signalr": "^1.0.0" npm package

const connection = new signalr.HubConnectionBuilder()
    .withUrl('url')
    .configureLogging(signalr.LogLevel.Information)
    .build()

connection.onclose(() => {
   // close logic goes here
})

Answer 3

If you are using hubs then implement the IDisconnect interface.

public class ChatHub : Hub, IDisconnect
{
    public void Disconnect()
    {
        Debug.WriteLine(Context.ConnectionId + " disconnected");
    }
}

On persistent connections you can override OnDisconnectAsync, (from the SignalR wiki at https://github.com/SignalR/SignalR/wiki/PersistentConnection )

public class MyEndPoint : PersistentConnection 
{
    protected override Task OnDisconnectAsync(string clientId) 
    {
        return Connection.Broadcast("Client " + clientId + " disconncted");   
    }
}

Answer 4

The SignalR 2.0 way of doing this is like so:

$.connection.hub.disconnected(function () {
    console.log('Connection disconnected')
});

http://www.asp.net/signalr/overview/signalr-20/hubs-api/hubs-api-guide-javascript-client#connectionlifetime