1. IoT with SignalR & .NET Gadgeteer
Internet of Things & .NET Gadgeteer & Microsoft SignalR Mirco Vanini
Microsoft® MVP Windows Embedded

2. Agenda
Perché real-time e come ? SignalR Connections and Hubs Clients Demo Q&A Links

3. Perché real-time e come ?
Gli utenti vogliono le ultime informazioni, ORA !
Twitter – live searches/updates
Stock streamers
Auctions
Live scores
Real-time notifications
Interactive games
Collaborative apps
Live user analytics

4. Perché real-time e come ?
HTTP is an old beast…
Never designed for real-time communications
Web is request-response
Web is stateless
HTML5 WebSockets to the rescue, right?
Extension to HTTP
Provide raw sockets over HTTP
Full-duplex
Traverses proxies
It’s still a draft…
Not every proxy server supports it
Not every webserver supports it
Not every browser supports it
They are raw sockets!  

5. Perché real-time e come ?
Come implementare il real-time con HTTP: Polling. Long Polling. Forever Frame. Server Sent Events

6. Perché real-time e come ?
Polling: the stubborn approach
Server
Response
Request
Client
delay
Time: requests event ‘n’ seconds (fixed time)
Twitter clients

7. Perché real-time e come ?
Polling
High overhead on requests: headers and such…
High overhead on response: same as before…
High latency.
Waste of bandwith.
Waste of resources.

8. Perché real-time e come ?
Long Polling: the kind gentleman approach
Server
Response
Request
Client
Variable delay
Time: requests event ‘n’ seconds (variable)
Facebook chat

9. Perché real-time e come ?
Long Polling (Hanging GET)
High overhead on requests: headers and such…
High overhead on response: same as before…
Medium latency.
Waste less of bandwith.
Waste of resources.
Better than the previous one: less requests

10. Perché real-time e come ?
Forever Frame
Server
HTTP/ OK Content-Type: text/plain Transfer-Encoding: chunked
Server tells client that response is chuncked
Client keeps connection open untill server closes it
Server pushes data to the client followed by \0
Consumes server threads
<script>eval("... ")</script>\0
<script>eval("... ")</script>\0
Client

11. Perché real-time e come ?
Server-Sent Events
Server-Sent Events (SSE) are a standard describing how servers can initiate data transmission towards clients once an initial client connection has been established. They are commonly used to send message updates or continuous data streams to a browser client and designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through which a client requests a particular URL in order to receive an event stream.
Stream Updates with Server-Sent Events

12. Real-time: How to survive ?
So many options and a big Headache !

13. SignalR Persistent Connection Abstraction communication library.
Abstracts protocol and transfer (choses the best one).
A single programming model (a unified development experience).
Extremely simple to use.
Server-side it can be hosted in different «environments» (ASP.NET, console apps, windows services, etc…).
Client-side there’s support for: Javascript clients, .NET clients, WP; provide by the community: iOS, Android.

14. Try WebSocket then fallback to:
SignalR
Works everywhere !!!
Try WebSocket then fallback to:
Server Sent Events
Forever Frame
Long Polling
Bet to keep the logic connection up include retry logic
Scale out to web-farms

15. SignalR
Complete rewrite of the internals for 1.0.0
Very hight performance on a single box ’s of messages per seconds
Very low memory overhead
Full async
1000’s of connection per server
Cross-platform: run it on OSX or Linux with Mono
Supported part of ASP.NET family

16. SignalR
Persistent Connections: «Low level» API, manages the connection and the «raw» stream of data.
Hubs: «High level» API, provide advanced support for internal routing (calling functions on server & clients), connection and disconnection tracking, grouping etc… Automatic client proxy generation (JavaScript)

17. SignalR Install-Package Microsoft.AspNet.SignalR
Install-Package Microsoft.AspNet.SignalR.Sample

18. SignalR packages Core Meta package Hosts
Microsoft.AspNet.SignalR.Core: Server side components needed to build SignalR endpoints
Meta package
Microsoft.AspNet.SignalR: - A meta package that brings in everything you need to run it on IIS and ASP.NET
Hosts
Microsoft.AspNet.SignalR.SystemWeb - Pulls in the required packages to host SignalR in ASP.NET (via OWIN ASP.NET host)
Microsoft.AspNet.SignalR.Owin - OWIN* host for SignalR
* OWIN stands for “Open Web Interface for .NET” and it is a specification for the communication between .NET Web Server and Web applications.

19. SignalR packages Clients Scaleout Buses Sample
Microsoft.AspNet.SignalR.Js - Javascript client for SignalR
Microsoft.AspNet.SignalR.Client - .NET client for SignalR (includes WinRT, Windows Phone 8 and Silverlight5 clients)
Scaleout Buses
Microsoft.AspNet.SignalR.Redis - Redis scaleout for SignalR
Microsoft.AspNet.SignalR.ServiceBus - Service bus scaleout for SignalR
Sample
Microsoft.AspNet.SignalR.Sample - A sample stock ticker you can quickly and easily bring into your app to get a working sample up and running.

20. Demo
Web Plant Monitor PlantHub PlantMonitor PlantManager Plant Device PlantCommand PlantData TcpCommandListener

21. Demo Data Flow HUB Device Page Page Page updatePlaintData SendCommand
21000
HUB
data
Device
command
22000
command
data
updatePlaintData
SendCommand
Page
Page
Page

22. Q&A

23. Links Getting Started with ASP.NET SignalR ASP.NET SignalR
Building Real-time Web Apps with ASP.NET SignalR
Engaging the Realtime Web with SignalR
SignalR. Code, not toothpaste.

24. Contatti
Blog Web