signalr programming by example pdf


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SignalR Programming in Microsoft Save this PDF as: . Also, because SignalR itself and many of the examples and contents are focused on the. Pro SignalR: Real-Time Communication with SignalR Copyright © by Keyvan .. Examples of Real–Time Web Application Development. NET programming, and contributed to several open-source projects. introduced SignalR, which is part of libraries. It uses existing transport Chat is the de-facto example of real-time technology as it requires . oriented programming interface which provides developer a lot of control.

It was initially defined in 1 simplicity and versatility of its design are, to an extent, responsible for the success and expansion of the Web and the Internet as a whole. Its operation is based on a request-response schema which is always started by the client. This procedure is often referred to as the Pull model: When a client needs to access a resource hosted by a server, it purposely initiates a connection to it and requests the desired information using the language defined by the HTTP protocol. The server processes this request, returns the resource that was asked for which may be the contents of an existing file or the result of running a process and the connection is instantly closed. If the client needs to obtain a new resource, the process starts again from the beginning: A connection to the server is opened, the request for the resource is sent, the server processes it, it returns the result and then closes the connection. This happens every time we access a webpage, images or other resources that are downloaded by the browser, to give a few examples. Figure 1. NET SignalR - Incredibly simple real-time features for your web apps As you can guess by looking at the image above, it is a synchronous process: After sending the request to the server, the client is left to wait, doing nothing until the response is available. Using AJAX techniques, the exchange of information between the client and the server can be done without leaving the current page. At any given moment, the client may initiate a connection to the server using JavaScript, request a resource and process it for example, updating part of the page. What is truly advantageous and has contributed to the emergence of very dynamic and interactive services, such as Facebook or Gmail, is that these operations are carried out asynchronously, that is, the user may keep using the system while the latter communicates with the server in the background to send or receive information. Figure 2. The client is always the one to take the initiative, deciding when to connect to the server. However, there are scenarios where HTTP is not very efficient. With this protocol it is not easy to implement instant-messaging applications or chat-rooms, collaboration tools, multiuser online games or real-time information services, even when using asynchrony.

There is a more conservative variant of polling, but it degrades user experience. It is the technique called piggy backing, which consists in not making deliberate queries from the client and, instead, taking advantage of any interaction between the user and the system to update any necessary information.

To illustrate this, consider a web mail service: Instead of making periodic queries to check for the arrival of new messages, 12 ASP. NET SignalR - Incredibly simple real-time features for your web apps those checks would be performed each time the user accessed a page, an email or any other feature. This may be useful in scenarios which do not require great immediacy and where the features of the system itself mean that we can be sure that the user will interact with the application frequently.

In conclusion, polling is a reasonable option despite its disadvantages when we want a solution that is easy to implement and able to be used universally and in scenarios where a very high update frequency is not required. A real-life example of its application is found in the Web version of Twitter, where polling is used to update the timeline every thirty seconds.

Among them, we can name instant-messaging systems, real-time collaboration toolsets, multiuser online games, information services and any kind of system where it is necessary to send information to the client right when it is generated. For such applications, we need the server to take the initiative and be capable of sending information to the client exactly when a relevant event occurs, instead of waiting for the client to request it.

And this is precisely the idea behind the Push, or Server Push, concept. This name does not make reference to a component, a technology or a protocol: it is a concept, a communication model between the client and the server where the latter is the one taking the initiative in communications. This concept is not new.

There are indeed protocols which are Push in concept, such as IRC, the protocol which rules the operation of classic chat-room services; or SMTP, the one in charge of coordinating email sending.

These were created before the term that identifies this type of communication was coined. For the server to be able to notify events in real time to a set of clients interested in receiving them, the ideal situation would be to be able to initiate a direct point-to-point connection with them. For example, a chat-room server would keep a list with the IP addresses of the connected clients and open a socket type connection to each of them to inform them of the arrival of a new message.

However, that is technically impossible. For security reasons, it is not normally possible to make a direct connection to a client computer due to the existence of multiple intermediate levels that would reject it, such as firewalls, routes or proxies.

For this reason, the customary practice is for clients to be the ones to initiate connections and not vice versa. In order to circumvent this issue and manage to obtain a similar effect, certain techniques emerged which were based on active elements embedded in webpages Java applets, Flash, Silverlight apps.

These components normally used sockets to open a persistent connection to the server.

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That is, a connection which would stay open for as long as the client was connected to the service, listening for anything that the server had to notify. When events occurred which were relevant to the client connected, the server would use this open channel to send the updates in real time. HTTP: You are the client, you are the boss 13 Although this approach has been used in many Push solutions, it is tending to disappear.

Active components embedded in pages are being eliminated from the Web at a dramatic speed and are being substituted for more modern, reliable and universal alternatives such as HTML5. Furthermore, long-term persistent connections based on sockets are problematic when there are intermediary elements firewalls, proxies which can block these communications or close the connections after a period of inactivity.

They may also pose security risks to servers. Given the need for reliable solutions to cover this type of scenarios, both W3C and IETFthe main organisms promoting and defining protocols, languages and standards for the Internet began to work on two standards which would allow a more direct and fluent communication from the server to the client. Basically, it allows the establishment of a persistent connection that the client will initiate whenever necessary and which will remain open.

A two-way channel between the client and the server is thus created, where either can send information to the other end at any time.

SignalR eBook | Hypertext Transfer Protocol | Web Server

Figure 4. Operation of the Websocket standard At the moment, the specifications of both the API and the protocol are in draft state, which means that we cannot consider the application of this technology to be universal. Some only feature partial implementations Opera, Safari and in others, Websocket is simply not available 2 Aside from the problem of the different implementation levels at the client side, the fact that the standard includes an independent protocol for communication although initially negotiated on HTTP means that changes also have to be made on some infrastructural elements, and even on servers, so that connections using Websocket are accepted.

NET Core. Read more. Product details Series: Developer Reference Paperback: Microsoft Press; 1 edition February 28, Language: English ISBN Tell the Publisher! I'd like to read this book on Kindle Don't have a Kindle? Share your thoughts with other customers. Write a customer review. Top Reviews Most recent Top Reviews. There was a problem filtering reviews right now.

Please try again later. Paperback Verified download. Helped me tremendously in getting to understand the SignalR framework. One person found this helpful. This book was exactly what I was looking for. It gave a good overview and enough detail to get me started.

Kindle Edition Verified download. Full coverage of all important topics. Well organised content and precise writing. Here I am developing an Azure Web service for synchronizing identities from on-premises sources with Azure Active Directory.

That's not at all the sort of Web-based user inter-communication problem that the developers of SignalR had in mind; it's neither Twitter nor Halo.

Yet, SignalR absorbs my non-functional requirements and complexity drains out of my code into its infrastructure. So, it's a technology with tremendous reach and impressive power. Aguilar's book is simply superb for the following reasons: It starts by stating the problem in general terms, describing the prior state of the art and explaining why SignalR is a profoundly good solution to the problem.

The reader is then taught the technology in sensible, easy to absorb stages with ideally simple snippets of code, culminating in more elaborate and satisfying complete applications at the end of each chapter, which are still simple, just a few pages long.

Although the complexity builds, the writing remains wonderfully simple. Although the complexity builds, Mr.

Aguilar never waves his hands: All aspects of the technology and related non-functional requirements are dealt with by the end of the book, at least as far as I can tell. Horizontal scaling? Writing unit tests? Check, with complete examples that mock everything that is not "under test. Yes, check that, too! The book also happens to be the very best guide to OWIN and Katana that is presently between two covers.

A reader can breeze through this in a couple of hours and still have most of the day to make money building powerful applications on top of SignalR! With plenty of examples, gotchas, and hands-on exercises, "SignalR Programming Almost all of the questions I had going into reading this book were answered sufficiently.

Very nice book that covers SignalR. I really like that it goes beyond the basic hub and code samples that demonstrates communicating between users that are registered with a specific hub.

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