Jun 23, 2016 07:43 AM|Fei Han - MSFT|LINK
Welcome to ASP.NET forum.
Each client connecting to a hub passes a unique connection id, if you’d like to broadcast message between two clients (one-to-one), you could refer to the following sample code to send a message to a specific user.
public class MyHub : Hub
public void Send(string userId, string message)