Understanding SignalR

The web is great for building general-purpose websites and services, but it was not designed for specialized scenarios that require a web page to be instantaneously updated with new information as it becomes available.

The history of real-time communication on the web

To understand the benefits of SignalR, it helps to know the history of HTTP and how organizations worked to make it better for real-time communication between clients and servers.

In the early days of the web in the 1990s, browsers had to make a full-page HTTP GET request to the web server to get fresh information to show to the visitor.

In late 1999, Microsoft released Internet Explorer 5.0 with a component named XMLHttpRequest that could make asynchronous HTTP calls in the background. This alongside dynamic HTML (DHTML) allowed parts of the web page to be updated with fresh data smoothly.

The benefits of this technique were obvious, and soon all browsers added the same component...