The Azure SignalR Service is a serverless offering from Microsoft to facilitate real-time communications without having to manage the infrastructure yourself. Azure SignalR Service provides a process of giving real-time web functionality (i.e. push updates to connected clients) to applications over HTTP protocol. The client gets updates without poll to the server (which means without refreshing the web page – here server push to a client as and when needed)
Generally, WebSocket is the optimal transport that is used, but, if a WebSocket connection cannot be established, the SignalR client will fall back to either Server-Sent Events or long polling.