namespace my.Server
{

public class myServer
{
//...
  public void chtoto_sluchilos()
  {
   // ... послать сообщение 
   // Send("", "уйдите на!")
  }
  public int ya_ushol(string name)
  {
    //
    return 2;
  }
}

 public class MyHub : Hub 
 {
        public void Send(string name, string message)
        {
            Clients.All.addMessage(name, message);
        }
        public override Task OnConnected()
        {
            Program.MainForm.WriteToConsole("Client connected: " + Context.ConnectionId);
            return base.OnConnected();
        }
        public override Task OnDisconnected()
        {
            Program.MainForm.WriteToConsole("Client disconnected: " + Context.ConnectionId);

            // ya_ushol("vasya");

            return base.OnDisconnected();
        }
    }
 }
}