Fair question, but it was one of those times when I decided I had to guess what the question meant. Obviously if I know what ports the instances use for their DACs I can connect to them using sqlcmd. Equally obviously I can discover the ports by looking at the SQL Server log for each instance, if I have access and know where it is. I'm one of those people who always has access to the SQL Server log directory for ech instance, and who decides where that directory will be.
But of course that can't be done by a DBA who insists on using SSMS.
I was feeling contrary this morning, so I picked "can't be done", although I know perfectly well that it can, and got my point.
Maybe the author of the question thought you had to have Service Broker to connect through DAC, rather than assuming one of those arrogant developer-hating sql-hating know-nothing DBAs? Well, I have Service Broker disabled and have connected using DAC both to default and to non-default instances (just to make sure I could safely disable service broker).