At the core of SignalR sits the abstraction that represents an actual connection. This is the lowest level of the abstraction and it is the thing that deals with connecting the client to the server and abstracting away the negotiation for protocol, and in general all communication. One could look at this as what is known as the socket connection in regular TCP/IP development. Although it is a bit easier, since you're not having to deal with byte buffers, but strings instead.