Building modern web sites with ASP .Net Web API, WebSockets and RSignal

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Building modern web sites with ASP .Net

Web API, WebSockets and RSignal

Alessandro PilottiMVP ASP.Net / IISWindows Azure Insider@alexpilotti


Mobile & DevelopmentITCamp 2012 sponsors


Mobile & Development

• ASP.Net Web API• SignalR• WebSocket

Agenda



• The web app designer’s holy grail:– Reach the usability level of a desktop app

• The web app designer’s curse:– Lack of standard API on the browser’s side

• Until recently the only way out was a RIA framework:– Flash / Silverlight

What’s the deal?



• HTML5 is changing the game• Great set of new browser features:– Application cache– Web storage– WebSockets– WebWorkers– Geolocation– Drag&Drop– Multiple file uploads– Inline SVG– History management– … and that Video thing

HTML5



• Javascript is getting a huge boost– There’s more than meets the eye– Its prototyping nature and flexibility is great

• The rest sucks

• An enormous amount of frameworks are available today, e.g:– JQuery / JQuery UI– Knockout.js– Backbone.js– Underscore.js– History.js– …And a gazillion more

Javascript?



• Single Page Applications– A single HTML is loaded in the browser– History (aka back button) is managed via

Javascript– Templates are used to load and render in

the DOM content on demand• Some Ajax might be useful for that

– Offline usage• Application cache• Web storage

SPA



• Web pages communicate with the server via asynchronous calls– XmlHttpRequest (as in ajax)– JSON serialization

• Way faster than XML• Originally decoded with “eval”• Modern browsers provide native encoding /

deconding– JSON.parse(…) / JSON.stringify(…) – Even faster!

– RESTful APIs –WebSockets

• Where supported

And how do we access Data?



• Faster web sites• Lower traffic• Clear separation– UI– Services / BL

• Enhanced testability– Unit tests for the server API– MVVM in Javascript (e.g. Knockout.js)

• Enhanced portability– E.g. Mobile UI

Great advantages



• ASP.Net Web API– Comes with MVC4– Provides a new RESTful Web API framework– ODATA support– Very easy– Great IoC support– EF integration (DbDataController<T>)– Can be also installed on MVC3 or Web Forms

• Install-Package AspNetWebApi

• All the ASP.Net Stack is open source!!– http://aspnetwebstack.codeplex.com/

• Alternative: WCF– RESTful support– More control

• Complicated bindings configuration

ASP.Net Web API

http://aspnetwebstack.codeplex.com/

http://aspnetwebstack.codeplex.com/



• Use of HTTP verbs:– GET– POST– PUT– DELETE

• Great for CRUD operations• Errors use HTTP semantics– E.g. not found => 404

• Uses custom routing• A lot less bloated than SOAP

RESTful APIs



Action HTTP verb Relative URI

Get a list of all products GET /api/products

Get a product by ID GET /api/products/id

Get a product by category GET /api/products?category=category

Create a new product POST /api/products

Update a product PUT /api/products/id

Delete a product DELETE /api/products/id

RESTful APIs example



jQuery does all the dirty job, the result is neat and clean:

$.getJSON( "api/products", function(data) { $.each(data, function(index, value) { $("#products").append('<li>' + value.Name + '</li>'); });

});

jQuery example



routes.MapHttpRoute( name: "API Default", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional });

• Avoids conflicts with MVC routing• Naming Convention

– GetAllProducts, DeleteProduct, etc

• Explicit action attributes:– [HttpGet], [HttpPost], [HttpPut], [HttpDelete], [NonAction]

• User "api/{controller}/{action}/{id}” for RPC style routing– Needs explicit verb attributes

ASP.Net Web API routing



• ASP.Net Web API is based on a pipeline• Inherit from DelegatingHandler to

create your handlers– E.g. check an API key

• Add with:– config.MessageHandlers.Add(new

ApiKeyHandler());

HttpMessageHandler



• Open Data Protocol– A web protocol for querying and updating data

• Enable ODATA queries on your Web API– Just return an IQueriable<T>

• Examples– http://localhost:1702/api/Products?$filter=Enabled

%20eq%20true

– http://localhost:1702/api/Products?$orderby=Name%20desc

– http://localhost:1702/api/Products?$filter=startswith(Name,’whatever')

ODATA + Web API



• Great tool for troubleshooting

• curl -i -H "Accept: application/json" http://localhost:1823/api/Products

• curl -i -H "Content-Type: application/json" -H "Accept: application/json" -X POST -d @data.json http://localhost:1823/api/Product

CURL


WEB API DEMO



• A framework that provides some magic for:– Persistent connections

• LongPolling• WebSockets• Examples: chat, stock ticker updates

– Dynamic proxy generation for Javascript code• Hubs

– JSON serialization

• Asynchronous model• Supports self hosting• Unrelated to MVC or Web Forms• Install-package SignalR

– Or: https://github.com/SignalR/SignalR

SignalR

https://github.com/SignalR/SignalR

https://github.com/SignalR/SignalR


Mobile & DevelopmentLong Polling

1. The client connects via HTTP2. The server waits for available data3. The server sends the response4. Back to step one

A way to simulate push data connections



public class MyConnection : PersistentConnection

{ protected override Task OnReceivedAsync(IRequest request, string connectionId, string data) { // Broadcast data to all clients return Connection.Broadcast(data); } }

Routing setup in global.asax:

RouteTable.Routes.MapConnection<MyConnection>("echo", "echo/{*operation}");

Persistent connections (server)



$(function () { var connection = $.connection('/echo');

connection.received(function (data) { $('#messages').append('<li>' + data + '</li>'); }); connection.start(); $("#broadcast").click(function () { connection.send($('#msg').val()); }); });

Persistent connections (client)



• Task OnConnectedAsync(IRequest request, string connectionId)

• Task OnReconnectedAsync(IRequest request, IEnumerable groups, string connectionId)

• Task OnReceivedAsync(IRequest request, string connectionId, string data)

• Task OnDisconnectAsync(string connectionId)

• Task OnErrorAsync(Exception error)

PersistentConnection API



• Task Broadcast(object value)• Task Send(string signal, object value)

IConnection API



var context = GlobalHost.ConnectionManager.GetConnectionContext<MyEndPoint>(); context.Connection.Broadcast(message);

• Useful to send messages starting from a server action

External broadcasts



public class Chat : Hub { public void Send(string message) { // Call the addMessage method on all clients Clients.addMessage(message); } }

• Methods can have any name, the client resolves the names via proxy

• Clients is a dynamic object– addMessage is defined in Javascript!!

Hub (server)



var chat = $.connection.chat; // Declare a function on the chat hub so the server can invoke it chat.addMessage = function(message) { $('#messages').append('<li>' + message + '</li>'); }; $("#broadcast").click(function () { // Call the chat method on the server chat.send($('#msg').val()) .done(function() { console.log('Success!'); }) .fail(function(e) { console.warn(e); }); }); // Start the connection $.connection.hub.start();

Hub (client)



• SignalR’s AspNetBootStrapper defines– [assembly:

PreApplicationStartMethod(typeof(AspNetBootstrapper), "Initialize")]

– Initialize calls: RouteTable.Routes.MapHubs();• Mapping the /signalr route

• No need for:– Explicit global.asax route mapping– Web.config settings

Look Mama, no global.asax routes



var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); context.Clients.say(message);

External broadcasts



• appcmd.exe set config /section:serverRuntime /appConcurrentRequestLimit:100000

• In %windir%\Microsoft.NET\Framework\v4.0.30319\aspnet.config– maxConcurrentRequestsPerCPU="20000”

• In %windir%\Microsoft.NET\Framework\v4.0.30319\Config\machine.config– <processModel autoConfig="false"

requestQueueLimit="250000" />

IIS setup for high loads


SIGNALR DEMO



• TCP/IP communication style model– Handshake resembles HTTP

• Interoperable• Standard W3C (still in draft)– Older browsers support old versions

• Bidirectional communications• Supports cross domain access!

WebSockets



Request:

GET /mychat HTTP/1.1Host: server.example.comUpgrade: websocketConnection: UpgradeSec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==Sec-WebSocket-Protocol: chatSec-WebSocket-Version: 13Origin: http://example.com

Response:

HTTP/1.1 101 Switching ProtocolsUpgrade: websocketConnection: UpgradeSec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=Sec-WebSocket-Protocol: chat

Handshake

http://example.com/

http://example.com/



• Url: ws://yourhost/etc– wss: when used with SSL/TLS

var socket = new WebSocket('ws://game.example.com:12010/updates');socket.onopen = function () { setInterval(function() { if (socket.bufferedAmount == 0) socket.send(getUpdateData()); }, 50);};

Javascript



• IE 10• Chrome 4• Firefox 4• Safari 5• Opera 11

• Server: IIS 8

Minimum requirements



• Proxies tipically don’t recognize WebSocket traffic

• By using SSL/TLS the problem is mitigated– Client uses HTTP CONNECT in this case

Proxy support



IIS 8 – enable WebSockets feature


Mobile & DevelopmentWCF 4.5 – HTTP Activation


Mobile & DevelopmentWCF 4.5



• Install-Package Microsoft.WebSockets

RouteTable.Routes.Add(new ServiceRoute("connect", new WebSocketServiceHostFactory(), typeof(GameService)));

public class GameService : WebSocketService { private static GameServer server = new GameServer();

private GameConnection connection;

public override void OnOpen() { string nickname = QueryParameters["nickname"]; int gameSize = int.Parse(QueryParameters["gamesize"]); connection = server.JoinGame(this, nickname, gameSize); }

public override void OnMessage(string message) { connection.ProcessCommand(message); }

protected override void OnClose() { if(connection != null) connection.Disconnect(); } }}

In ASP.Net – updated support


WEBSOCKETS DEMO


Q & A

Technology

Building modern web sites with ASP .Net Web API, WebSockets and RSignal