Real-time Web applications feature the ability to push server-side content to the connected clients as it happens, in real-time. For ASP.NET developers, ASP.NET SignalR is a library to add real-time web functionality to their applications. It takes advantage of several transports, automatically selecting the best available transport given the client and server’s best available transport. It takes advantage of WebSocket, an HTML5 API that enables bi-directional communication between the browser and server.
SignalR also provides a simple, high-level API for doing server to client RPC (call JavaScript functions in your clients’ browsers from server-side .NET code) in your ASP.NET application, as well as adding useful hooks for connection management, such as connect/disconnect events, grouping connections, and authorization.