1. Real-time Communications
with SignalR
Shravan Kumar Kasagoni

2. Agenda
1) Introduction to the real-time web
2) ASP.NET SignalR
3) Building a real-time

3. Real-time Application?
Real-time functionality is the ability to have server code
push content to connected clients instantly as it becomes
available, rather than having the server wait for a client
to request new data.

4. Without real-time

5. With real-time

6. Why Real-time?
Users want the latest info, NOW!

7. Show Me Some Examples
 Twitter, Facebook, Mail - live searches/updates
 Stock streamers
 Auctions
 Interactive games
 Live Scores
 Collaborative apps (google docs, office web
apps)
 Live user analytics (live graphs)

8. How to build real-time web apps?

9. HTTP is an old beast…
Never designed for real-time communications
 Web is all about request-response
 Web is stateless

10. How to do real-time in web?

11. Periodic polling
 Poll from time to time using Ajax
 Delay in communication due to polling interval
 Wastes bandwidth & latency
Server
Client
Polling interval

12. Long polling
 Poll but doesn’t respond until there's data
 Poll again after data received or after the connection
times out
 Consumes server & threads & connection resources
Server
Client

13. Forever Frame
 Server tells client that response is chucked
 Client keeps connection open until server closes it
 Server pushed data to the client followed by 0
 Consumes server threads
Server
Client

14. HTML5 Web sockets
 Extension to HTTP
 Provides raw sockets over HTTP
 Full-duplex
 Traverses proxies
 It's still a working draft
 Not every proxy server supports it
 Not every web server supports it
 Not every browser supports it
 They are raw sockets!

15. too many options

17. Basically…

18. Introducing SignalR
• Abstraction over transports
• Events instead of task/async
• Connection management
• Broadcast or target specific client

19. What does SignalR do?
• Client to Server persistent connection over HTTP
• Easily build multi-user, real-time web applications
• Auto-negotiates transport

20. SignalR Fallback
Long
Polling
Forever
Frames
Server
Sent
Events
Web
Sockets

21. What does SignalR do?
• Allows server-to-client push and RPC
• Built async to scale to 1000’s of connections
• Scale out with Service Bus,
SQL Server & Redis
• Open Source on GitHub

22. Backplane
SignalR Backplanes
Load balancing via a common transport mechanism

23. Thank You