When learning a brand-new code library, you might initially think that it is great and you will use it for every project going forward. Although sometimes the new library will work in your latest project, it is probably not the best solution. This chapter discusses the technologies on which ASP.NET SignalR is built. These are the technologies that enable SignalR to support a wide range of server and client platforms. Because you'll be eager to try SignalR, you will write your first SignalR application. After creating the first application, the focus is on when it is best to use SignalR.