SignalR

SignalR is the open-source library for ASP.NET Core that enables instant, bidirectional server-to-client content push, abstracting real-time communication protocols.

SignalR establishes a persistent, full-duplex connection between server and client, moving beyond the classic HTTP request-response model. It automatically manages transport fallback, prioritizing WebSockets (for optimal efficiency) and gracefully falling back to Server-Sent Events or Long Polling as necessary. The high-level API, Hubs, facilitates seamless Remote Procedure Calls (RPC): server-side .NET code can instantly invoke client-side JavaScript functions, and vice-versa. This capability is critical for high-frequency updates in applications like live chat, real-time stock dashboards, and collaborative document editing.

https://learn.microsoft.com/en-us/aspnet/core/signalr/