SignalR - Realtime client/server communication (iSense)

1. SignalR Realtime client/server communication Maarten Balliauw @maartenballiauw
2. R
3. Who am I? Maarten Balliauw Antwerp, Belgium Developer Advocate, JetBrains Founder, MyGet AZUG Focus on web ASP.NET MVC, Azure, SignalR, ... Former MVP Azure & ASPInsider Big passion: Azure http://blog.maartenballiauw.be @maartenballiauw
4. Agenda Why real-time & how? Meet SignalR Connections and Hubs Clients .NET Core Q&A
5. Why real-time & how?
6. Users want the latest info, now! Twitter – live searches/updates Stock tickers Auctions Live scores Real-time notifications Collaborative apps Live user analytics Online gaming / browser games … 6
7. HTTP is and old beast Never designed for real-time communications Web is request-response Web is stateless Websockets to the rescue!
8. Websockets Extension to HTTP Provide raw sockets over HTTP Full-duplex, low latency Traverses proxies But… Not every proxy server supports it Not every webserver supports it Not every browser supports it Some antivirus blocks it They are raw sockets! (protocol: up to you) http://websocketstest.com/
9. Forever Frame 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 HTTP/1.1 200 OK Content-Type: text/plain Transfer-Encoding: chunked <script>eval("... ")</script>0 <script>eval("... ")</script>0
10. Periodic polling Poll from time to time using Ajax Delay in communications due to polling interval Wastes bandwidth & latency  Polling interval
11. Long polling Poll but don’t respond until there’s data Poll again after data received or after the connection times out Consumes server threads & connection resources 
12. Options! Forever Frame Periodic polling Long polling Websockets (Server-Sent events)
13. SignalR
14. SignalR Three-in-one! “Persistent” client/server connection over best transport Connection negotiation Abstracts away the transport Provides just one programming model http://github.com/signalr/signalr - open source C#, JavaScript, UWP https://github.com/aspnet/signalr - new .NET Core version
15. Hello, SignalR DEMO
16. What just happened? The server is broadcasting a message every few seconds Clients are receiving messages Code looks easy No polling or whatsoever (at least not in my code) SignalR decides on transport mechanism used based on client + server
17. Connections and Hubs
18. Two programming models PERSISTENT CONNECTION Can communicate with 1..N clients Requires a route to be defined Limited to sending messages You define the “protocol” HUB Abstraction over PersistentConnection Can communicate with 1..N clients Route automatically mapped (/signalr/hubs) Can send messages and call methods SignalR defines the protocol
19. Hello, Hubs DEMO
20. Hubs Hub methods can be called from client Client methods can be called from hub Target individual client Target all clients Target group of clients http://shootr.signalr.net/
21. Clients
22. So far we have used... On the server side Host in any ASP.NET application (SignalR.Server) On the client side JavaScript (SignalR.JS) But there’s more…
23. Connecting to SignalR DEMO
24. There is more! On the server side Host in any ASP.NET application (SignalR.Server) or using self-hosting (OWIN based) Host on Azure Scale out (Redis, Azure Service Bus) (I did a NodeJS server as well, but don’t use it in production) On the client side JavaScript (SignalR.JS), Angular (AngularJs.SignalR.Hub) Any .NET client (SignalR.Client) UWP iOS Android
25. DeckCast DEMO
26. .NET Core
27. ASP.NET Core Sockets SignalR in the ASP.NET Core world Improvements based on SignalR learnings: No more jQuery No more iframe transport No more message replay after reconnect (memory usage, performance) No more Hub-state (I did not talk about this “ViewState” because it’s evil) Endpoint per Hub (/signalr/hubs  /signalr/...) Scale-out now becomes scale-out (and not sending all messages everywhere) Sticky sessions required (sad )
28. ASP.NET Core Sockets New features: Cross-platform (including things like RaspberryPi) Binary data support (think sending images etc.) Host-agnostic (HTTP works but also TCP/UDP/... sockets) Protocol data format pluggable (JSON, protobuf, ...) TypeScript client ...
29. Demo? Will leave this one for you... Under development! https://github.com/aspnet/signalr Preview release mid-year Release later this year
30. Conclusion
31. Conclusion SignalR is three-in-one! “Persistent” client/server connection over best transport Abstracts away the transport Provides just one programming model Connections & Hubs Connect various clients
32. Thank you! http://blog.maartenballiauw.be @maartenballiauw

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Open VS2017
Create a new ASP.NET Empty Website
Install-Package Microsoft.AspNet.SignalR
Note server library, client script, jQuery dependency
Add startup class:
public class Startup
{
public void Configuration(IAppBuilder app)
{
app.MapSignalR(); }
}
Add a class:
public class TimeConnection
: PersistentConnection
{
}
Map the connection:
app.MapSignalR<TimeConnection>("/time");
Add an infinite loop:
ThreadPool.QueueUserWorkItem(_ =>
{
var connection = GlobalHost.ConnectionManager.GetConnectionContext<TimeConnection>();
while (true)
{
connection.Connection.Broadcast(DateTime.UtcNow.ToString());
Thread.Sleep(1000);
}
});
Add some HTML:
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<script src="Scripts/jquery-1.6.4.min.js" type="text/javascript"></script>
<script src="Scripts/jquery.signalR-2.2.1.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function () {
var connection = $.connection('time');

connection.received(function(data) {
$('h1').text('The time is ' + data);
});

connection.start();
});
</script>
</head>
<body>
<h1>The time is now!</h1>
</body>
</html>
Now let’s take things easy… How does all of this work?
Note that we are sending data TO THE CLIENT by just broadcasting on the connection
View Chrome developer tools, in this case web sockets
Add to web.config: (.vs\config\applicationhost.config)
<system.webServer>
<webSocket enabled="false"/>
</system.webServer>
View Chrome again, notice now event stream is used instead

Install-Package Microsoft.AspNet.SignalR.Sample and show stock ticker in two browsers
Add simple chat hub
[HubName("simplechat")]
public class SimpleChatHub : Hub
{
private static readonly Dictionary<string, string> _users = new Dictionary<string, string>();

public async Task Join(string username)
{
_users[Context.ConnectionId] = username;

await Clients.All.userJoined(username);
}

public async Task SendMessage(string message)
{
await Clients.All.messageReceived(
_users[Context.ConnectionId], message);
}
}
Explain: user joins, we store username passed linked to connection id
We then call back to all clients, calling a JS function on there
Client code:
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<script src="Scripts/jquery-1.6.4.min.js" type="text/javascript"></script>
<script src="Scripts/jquery.signalR-2.2.1.min.js" type="text/javascript"></script>

<script src="/signalr/hubs"></script>
<script type="text/javascript">
$(function () {
var username = prompt('What is your name?');
$.connection.hub.logging = true;
var hub = $.connection.simplechat;

// User joined
hub.client.userJoined = function (who) {
$("#messages").append('<li><em>' + who + ' joined the chat.</em></li>');
};

// Message received
hub.client.messageReceived = function (who, what) {
$("#messages").append('<li>' + who + ': ' + what + '</li>');
};

// Join the chat
$.connection.hub.start().done(function () {
hub.server.join(username);
});

// Bind client UI
$('#message').change(function () {
hub.server.sendMessage($('#message').val());

$('#message').val('');
$('#message').focus();
});
});
</script>
</head>
<body>
<h1>Chat</h1>
<ul id="messages"></ul>
<input type="text" id="message"/>
</body>
</html>
Explore hubs some more: different properties on the hub (clients all, per group, individual, ...)
Create a new Console application
Install-Package Microsoft.AspNet.SignalR.Client
Add code
var connection = new Connection("http://localhost:51736/time");
connection.Received += data =>
{
Console.Clear();
Console.WriteLine(data);
};
connection.Start();

Cool, so connection works! Now let’s try hubs and connect to our simple chat.
Add code
private static async Task RunAsync(string[] args)
{
_connection = new HubConnection("http://localhost:51736/signalr");

_hub = _connection.CreateHubProxy("simplechat");

_hub.On <string>("userJoined", userName =>
{
Console.ForegroundColor = ConsoleColor.DarkYellow;
Console.WriteLine($"{userName} joined.");
Console.ResetColor();
});

_hub.On<string, string>("messageReceived", (userName, message) =>
{
Console.ForegroundColor = ConsoleColor.Yellow;
Console.WriteLine($"{userName}: {message}");
Console.ResetColor();
});

await _connection.Start();

// Join the chat
Console.WriteLine("Your username:");
var myName = Console.ReadLine().Trim();

await _hub.Invoke("join", myName);

// Send messages
while (true)
{
var myMessage = Console.ReadLine().Trim();
if (!string.IsNullOrEmpty(myMessage))
{
await _hub.Invoke("sendMessage", myMessage);
}
}
}
Open DeckCast
Show people around and tell them about deck.js
Show the presenter mode and client mode on the web
Start a console based viewer
Start a console based presenter

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