WebSockets

A WebSocket is a single long-lived TCP connection that lets a server push data to a client and the client send data back, both at any time, without the request-response shape that HTTP forces on you. The protocol starts as an HTTP request, gets upgraded to its own framed message protocol, and then stays open until one side closes it. This lesson covers why WebSockets exist, the upgrade handshake, the frame model, the C# client API (System.Net.WebSockets.ClientWebSocket), the server side in ASP.NET Core, the patterns for sending and receiving messages cleanly, the close handshake, and the cases where WebSockets are the wrong tool.