Some web applications application need to show data in real-time. As soon as the data is made available at the server, it immediately needs to be displayed to the end user. Traditionally developers used to poll the server periodically to check if a new data is available. This approach has its own drawbacks and may prove to be unsuitable in certain cases. Wouldn't it be nice if server notifies the client of new data rather than client checking with the server periodically? That is what HTML5 Server Sent Events (SSE) allow you to do. In this article you will learn what Server Sent Events or SSEs are and how to develop a ASP.NET Core application that receives real-time data from the server.