This document discusses SignalR, a Microsoft technology for building real-time web applications. SignalR provides a simple abstraction over various transport mechanisms like websockets, server-sent events, and long polling. It allows for easy implementation of real-time features like chat, live dashboards, and games. The document covers key aspects of SignalR like hubs for defining server-side endpoints, group management, authentication, and deployment options on web farms using Redis or SQL Server.

1. Alex Konduforov

2. About me
 Live in Kharkov
 Work at AltexSoft
 Blogger (merle-amber.blogspot.com)
 Speaker at different conferences
and .NET user groups
 Kharkov AI club co-organizer

3. Web evolution
Event-based, real-time UI
Partial page updates (Ajax), RIA
Dynamic pages, forms
Static HTML pages

4. Users Want the
Latest Info
NOW!

5. Social networks

6. Auctions

7. Stock tickers

8. Web chats

9. Other applications
 Live scores
 Real-time notifications
 Interactive games
 Collaborative apps
 Live user analytics
 etc.

10. Standard solutions
 Frequent Polling
 Long polling
 Server-Sent events (HTML5)
 WebSocket (HTML5)

11. Polling
 Get updates frequently using Ajax requests
Pros:
 --Cons:
 Delay in results
 Wastes bandwidth & latency

12. Long polling
 Similar to usual polling (Ajax requests)
 Request waits longer (1-2 minutes)
Pros:
 Lower load on server
 No delays
Cons:
 Consumes server threads & connection resources

13. Server-Sent events
 HTML5, works over HTTP
 EventSource JavaScript API
 Content-type: text/event-stream
Pros:
 No need to reconnect
 No need in a special protocol or server implementation
Cons:
 Works in server-t0-client direction

14. WebSocket
 HTML5, new protocol (ws:// and wss://) on top of TCP
Pros:
 Full-duplex persistent connection (both ways)
Cons:
 Require Web Socket protocol support on client (IE10)
 Require Web Socket protocol support on server (IIS8)

15. What to do?
WebSocket
Best solution
Not supported on all
browsers and server
Server-Sent events + Very good
Ajax to send data
Long Polling
Not so good
Not supported in IE
(damn!)
Supported everywhere
Mix
Do I need to implement
it on my own???
Very good

16. Superman SignalR to the rescue!

17. Authors
Damian Edwards
David Fowler

18. What is SignalR?
 Official MS technology to build real-time multi-user
ASP.NET applications: http://signalr.net/
 Out-of-box solution that consists of server and client
side
 Abstraction over the set of transports
 Open-source solution available on GitHub that can be
installed via NuGet

19. Transports priority
WebSockets
Server-Sent events
Forever Frame (IE hack)
Long Polling

20. Architecture
Client side
JS, .NET/WinRT, WP, Silverlight, iOS/Android
Hub API
PersistentConnection API

21. Hubs
 High-level API
 Similar to Controller (actions, thread per call)

22. Supported scenarios
 Client calling the server
 Server calling clients (all, group, one)
 State round-tripping between client and server
 Binding complex objects (JSON)
 Detecting connect, disconnect and reconnect clients
 Broadcasting from outside of a Hub
 Async scenarios (return Task/Task<T> to client)

23. Server calling the client
 dynamic Clients property
 JSON serialization

24. Managing Groups
 Add/remove connections to groups

25. Broadcasting from outside
 Notify clients from another server-side code

26. JavaScript client
 $.connection.hub

connection for all hubs (url points to /signalr)
 $.connection.hub.id

client id for the hub connection
 $.connection.hub.start()

starts the connection for all hubs
 $.connection.{hubname}

access a client side hub from the generated proxy

27. Exposing methods on the client
 The JavaScript client can declare methods that the
server can invoke:
 myHub.{method} = callback
 declares a function the server can invoke.
 method - name of the client side method
 callback - function to execute when the server invokes
the method

28. JavaScript example

29. Asynchronous execution

30. DEMO

31. Authentication
 Uses ASP.NET authentication mechanisms
 Provides the Authorize attribute for Hubs
 Forms and Windows authentications
 Certificates are available as well

32. Authentication
 Connection token uniquely identifies clients

33. Security
 Cross-Site Request Forgery (CSRF) prevention
 Disable cross domain requests
 Pass connection token in query string, not cookie
 Verify connection token
 If authenticated user changes,
SignalR requires a re-connection

34. Configuring SignalR
Set in IConfigurationManager:
Settings
Description
ConnectionTimeout amount of time to leave a connection
open (110 sec default)
Default value
110 seconds
DisconnectTimeout
amount of time to wait after a
20 seconds
connection goes away before raising the
disconnect event
HeartBeatInterval
interval for checking the state of a
connection
KeepAlive
amount of time to wait before sending a 30 seconds
keep alive packet over an idle
connection. Set to null to disable keep
alive
10 seconds

35. SignalR and web farm
 Azure Service Bus
 Windows Server Service Bus
 SQL Server
 Redis

36. SignalR over Redis
 Step 1

Download and install Redis as Windows service
 Step 2

Install-Package SignalR.Redis
 Step 3

37. New features in v2.0
 .NET 4.5 only!
 iOS and Android support via Xamarin
 Portable .NET clients
 Self hosting package
 Backwards compatibility server support
 Cross domain support
 Easier unit testing
 JavaScript error handling
 New HubException exception

38. Safe to use?
 Version 2.0 released
 Dynamically evolving
 Proven and stable technology
 Used in many real-time .NET applications
 Open-source

39. Materials
 https://github.com/SignalR
 http://jabbr.net
 http://www.hanselman.com/blog/CategoryView.aspx?cate
gory=SignalR
 http://www.asp.net/signalr/overview/signalr-20
 http://merle-amber.blogspot.com/2012/11/real-timeaspnet-signalr.html

40. Thanks for listening!
 merle-amber.blogspot.com
 aikharkov.wordpress.com
 @konduforov
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