Broadcasting from outside a Hub
All the recipes we illustrated so far have a common workflow as follows:
A client starts a connection first
The same client calls at least one method on the Hub
Eventually, any sequence of client-to-server and server-to-client calls can happen
Given the precondition of starting a connection from the client, which cannot be skipped, the fact that we then need at least one client-to-server call at the beginning, before doing anything else, may not be ideal. What if we want to start a conversation directly from a Hub? There's no such limitation with SignalR. In fact, a Hub may well be the first one to call back into the clients (already connected). There are a couple of ways to do it: the first one involves connection events, which will be illustrated in Chapter 6, Handling Connections, while the other option is based on the fact that a Hub can be used by any server-side code outside the Hub itself. This indeed becomes a mechanism to perform server-to-client calls...
