If you are not aware, to ensure communications of messages, SignalR uses three techniques (found across browsers) [ in this order ];
- ServerSideEvents (support in other browsers): Also called Event Source. It’s a push technology for sending notifications from the server to a client in the form of DOM Events.
- ForeverFrames (support in IE): This makes use of Chunking as found in the HTTP specification, but simiplistically is a Hidden iFrame in a Page that maintains a long-lived connection. Chunking is the process of breaking down large data and sending it incrementally and that same concept exists here with the Hidden iFrame.
- Long Polling: Like Polling except the server does not return to client until it is complete (getting the data)
So it will make use of each of these 4 technologies as it sees fit, where it is supported or not.
Hope this helps.