In domain mode there are many servers so you have to address the one you want to shutdown.
You have to connect the domain controller (master) and send the commands here.
a few examples if you start a domain of a fresh AS7:
/host=master:shutdown => stop the domain controller
/host=slave:shutdown => stop the slave host controller if you have such second instance running in the same domain
/host=master/server-config=server-one:stop
The given server instance (here server-one) is stopped, but not removed from config, so if you re-start the domain the server is up again