ASP.NET SignalR is a library for ASP.NET developers that makes it incredibly simple to add real-time web functionality to your applications.
What is "real-time web" functionality? It's the ability to have your server-side code push content to the connected clients as it happens, in real-time. You may have heard of WebSockets, a new HTML5 API that enables bi-directional communication between the browser and server.
SignalR will use WebSockets under the covers when it's available, and gracefully fallback to other techniques and technologies when it isn't, while your application code stays the same. SignalR also provides a very 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, e.g. connect/disconnect events, grouping connections, authorization.
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