Table Of ContentSignalR on .NET 6 - the Complete Guide
The easiest way to enable real-time two-way HTTP
communication on .NET 6
Fiodar Sazanavets
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Contents
1-IntroductiontoSignalR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
WhatmakesSignalRsogreat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ExampleusecasesforSignalR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Whoisthisbookfor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Thescopeofthisbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Howtousethisbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Bookstructure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Abouttheauthor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Gettingtouchwiththeauthor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2-Settingupyourproject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Settingupyourenvironment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
SettingupSignalRhub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
MakingSignalRhubstrongly-typed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3-In-browserSignalRclients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
SettingupJavaScriptclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
SettingupBlazorWebAssemblyclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4-ExternalSignalRclients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Settingup.NETclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
SettingupJavaclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
SettinguparawWebSocketclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
CONTENTS
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5-Sendingmessagestoindividualclientsorgroupsofclients . . . . . . . . . . . . . . . . . . 50
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Broadcastingmessagestoallclients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Sendingmessagestospecificclients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Workingwithclientgroups. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
6-StreaminginSignalR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Whatisstreamingusedfor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
ClientstreaminginSignalR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
ServerstreaminginSignalR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
7-AdvancedSignalRconfiguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
ConfiguringSignalRserver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
ConfiguringSignalRclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
ProsandconsofMessagePackprotocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
8-SecuringyourSignalRapplications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
WhatisCORSandwhyit’simportant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Settingupsinglesign-onprovider. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
ApplyingauthenticationinSignalR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
ApplyingauthorizationinSignalR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
9-ScalingoutSignalRapplication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
SettingupRedisbackplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
RunningmultiplehubinstancesviaRedisbackplane . . . . . . . . . . . . . . . . . . . . . . . 140
CONTENTS
UsingHubContexttosendmessagesfromoutsideSignalRhub . . . . . . . . . . . . . . . . . 144
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
10-IntroducingAzureSignalRService . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
SettingupAzureSignalRService . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
AddingAzureSignalRServicedependenciestoyourapplication . . . . . . . . . . . . . . . . 150
OverviewofAzureSignalRServiceRESTAPI . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Testyourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Furtherreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Wrappingup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Answerstoself-assessmentquestions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Chapter7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Chapter8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Chapter9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Chapter10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
1 - Introduction to SignalR
Ifyouareasoftwaredeveloperwhobuildsweb,mobileorinternetofthings(IoT)applications,you
will appreciate how important it is for your applications to have the ability to communicate with
the server asynchronously and in real time. Also, you probably realize that the standard request-
response model of communication isn’t fully suitable for modern apps. Sometimes, your client
application(whetherit’sawebpage,amobileapporaserviceonanIoTdevice)needstobeableto
receiveareal-timeupdatefromtheserverthatwasactuallytriggeredbyaneventontheserverand
notbyaclientrequest.
Weseethisfunctionalityeverywhere.Whenyouuseamessengerapp,youwouldexpecttoreceive
a message as soon as someone has sent you one. When you control your IoT devices, you expect
themtorespondtoyourcommandsassoonasyoutriggerthem.
Buttheproblemwithsuchfunctionalityisthatthesaidfunctionalityisnotalwayseasytoimplement.
Youcouldstillusetheclassicrequest-responsemodelandjustcarryonsendingrequeststotheserver
untilyoureceivearighttypeofresponse.Butthiswouldbewasteful.And,ifyourclientapplication
haslimitedbandwidthtoworkwith,youmaynotevenbeabletodoitatall,ascontinuousrequests
to the server may end up using up the entire bandwidth really quickly. As well as all of this, your
codetoimplementsuchabehaviorwouldprobablybewaymorecomplicatedthanitshouldbe.
There is also an alternative - WebSocket protocol. This is a much better solution. The protocol was
specifically designed to enable two-way communication between the client and the server. All you
have to do is establish a connection between the two endpoints. And, as long as this connection is
live,themessagescanflowbothways.Aswellassendinganyarbitrarymessagefromtheclientto
theserver,youcanalsosendmessagesfromtheservertotheclient.And,ontopofthis,WebSocket
protocolisveryefficient.Maintainingtheconnectiondoesn’tusemuchbandwidthatall.
However,WebSocketdoesn’tcomewithoutitsownproblems.It’sfarfrombeingtheeasiestthingto
workwith.Outofthebox,WebSocketprotocolusesrawdatainsteadofhuman-readableabstractions.
Ittransmitsmessagesbyusingrawbytes.So,it’suptoyoutodoalltheassemblinganddisassembling
of messages. It’s also up to you to monitor the state of the connection. The WebSocket code you’ll
havetowritewillprobablylooksimilartothis,whichisneitherveryintuitivenoreasilyreadable:
1-IntroductiontoSignalR 2
Figure1.1-WebSocketimplementationexample
Butifyouare.NETdeveloper,youwon’thavetodealwithanyofthis.Enablingefficientreal-time
two-way communication will almost be as easy as making classes inside a single application call
each other’s methods. And all of this was made possible with a help of a library called SignalR,
whichisoneofthein-builtlibrariesof AS.NETCore.
What makes SignalR so great
SignalR is a library that is incredibly easy to implement compared to the alternatives. Using this
library is just as easy as writing remote procedure calls. You will have some endpoint methods on
your server that are just bog-standard C# methods. And, as long as you specify the methods of the
same names on the client and put the expected parameters into them, the connection will be made
andthemethodwillbetriggered.
Same applies the other way round. Yourclient will haveeventlisteners with arbitrary names. And,
as long as you spell the name of the listener correctly in your server-side code and apply expected
datatypesasparameters,thelistenerontheclientwillbetriggered.
Forexample,yourserver-sidemethodmaylooklikethis:
1-IntroductiontoSignalR 3
Figure1.2-Server-sideSignalRmethod
Andyourclientcodethatwilltriggerthismethodmaylooklikethis:
Figure1.3-Client-sideSignalRmethodinvocation
Under the hood, SignalR library uses WebSocket protocol. But you, as a developer, don’t have to
worry about implementation details of it. Those are abstracted away to make things as convenient
foryouaspossible.
But WebSocket is not the only protocol that SignalR uses, even though it is the default protocol it
will try to use. It just happens that, although there aren’t many use cases where you won’t be able
touseWebSocket,occasionallyyoumayencountersuchasituation.AndthisiswhySignalRcomes
with two fallback protocols, which are server-sent events and long polling. The fallback order is as
follows:
1. Ifpossible,useWebSocket
2. IfWebSocketcan’tbeused,useserver-sentevents
3. Ifserver-senteventscan’tbeused,uselongpolling
Longpollingistheleastefficientprotocolofthemall.ThisiswheretheclientsendsastandardHTTP
request to the server and just waits until the response is sent back. This is why you won’t be using
thisprotocoluntilabsolutelynecessary.Butthemainbenefitofitisthatabsolutelyanysystemthat
supportsHTTPsupportslongpolling.
If you need to, you can even explicitly specify the protocol in the client configuration. But in most
cases,youwon’thaveto.Butevenifyoudo,thechoiceoftheprotocolwillhavezeroimpactonthe
wayyouwriteyourcode.Allyourcodewillbeidenticalregardlessoftheprotocolbeingused.
Example use cases for SignalR
SignalRisaperfectlibrarytobeusedinanyscenarioswhereclientsneedtoreceivereal-timeupdates
fromtheserverorthereishighahighfrequencyofdataexchangebetweentheclientandtheserver.
Aspertheofficialdocumentation¹,thefollowingaresomeoftheexampleswhereSignalRisanideal
librarytouse:
¹https://docs.microsoft.com/en-us/azure/azure-signalr/signalr-overview
1-IntroductiontoSignalR 4
• Highfrequencydataupdates:gaming,voting,polling,auction.
• Dashboardsandmonitoring:companydashboard,financialmarketdata,instantsalesupdate,
multi-playergameleaderboard,andIoTmonitoring.
• Chat:livechatroom,chatbot,on-linecustomersupport,real-timeshoppingassistant,messen-
ger,in-gamechat,andsoon.
• Real-time location on map: logistic tracking, delivery status tracking, transportation status
updates,GPSapps.
• Realtimetargetedads:personalizedrealtimepushadsandoffers,interactiveads.
• Collaborativeapps:coauthoring,whiteboardappsandteammeetingsoftware.
• Pushnotifications:socialnetwork,email,game,travelalert.
• Real-time broadcasting: live audio/video broadcasting, live captioning, translating,
events/newsbroadcasting.
• IoT and connected devices: real-time IoT metrics, remote control, real-time status, and
locationtracking.
• Automation:real-timetriggerfromupstreamevents.
Who is this book for
This book will be useful to any ASP.NET Core developer who is interested in enabling real-time
two-way communication between the clients and the server. Whether you are building a real-time
chatapplication,amessengerapp,oranIoTcontrolhub,youwillfindtheinformationinthisbook
useful.
The scope of this book
ThisbookwillteachyoueverythingyouwillneedtoknowaboutSignalR,soyouwillbeabletouse
itinanytypeofprojectwhereitcanprovidebenefits.Wewon’tgotoodeepintotheinnerworkings
of the library, but we will cover enough so you know how to use it in the most optimal way. We
willevencoversomeusecasesthataren’tofficiallydocumented,butthatmayactuallyhappen.For
example,youwilllearnhowtoconnectarawWebSocketclienttotheSignalRserverhub.Thisisa
usecaseIhavepersonallydealtwithinoneofmyprojects.
Another topic that we will address is how to integrate the latest .NET 6 and C# 10 features with
SignalR.ThereisawealthofinformationonlineonhowtouseSignalR,butsince.NET6isrelatively
recent, there isn’t much information on how to take advantage of the latest .NET 6 features while
usingit.Andthisbookisaimingtoaddressthisgap.
In this book, you will be working on the same .NET solution throughout the chapters, adding new
features to it as you go along. All the code samples used in the book are available in this GitHub
repo:
https://github.com/fiodarsazanavets/SignalR-on-.NET-6---the-complete-guide
