ASP.NET SignalR is a new library for ASP.NET developers that simplifies the process of adding real-time web functionality to your applications. Real-time web functionality is the ability to have server-side code push content to connected clients instantly as it becomes available.
You may have heard of the HTML5 WebSocket API that enables efficient bidirectional communication between the browser and server. SignalR uses Websockets when it is supported by the browser and the server, and gracefully falls back to other techniques and technologies when it is not. Either way, your application code stays the same.
SignalR provides a simple ASP.NET API for creating server-to-client remote procedure calls (RPC) that call JavaScript functions in client browsers from server-side .NET code. SignalR also includes API for connection management (for instance, connect and disconnect events), grouping connections, and authorization.
http://www.asp.net/signalr
