We didn't get things quite right with the shell in M6. My apologies for that.
We added the new shell that's ssh based and had intended it to run alongside the old telnet one with the ssh shell being available at shell.port +1, i.e. 2402 by default. We got the ssh bit right, so it is available on 2402, but neglected to keep the telnet console in place. In short, if you ssh to port 2402 the new shell should be available. By default the username is admin and the password is springsource. You can also access the shell in process by starting dm Server will -shell.
We've done a lot of work on the shell since M6, including adding tab completion, and reworking the command structure. If you're interested in looking at what the shell has to offer, I'd recommend grabbing a recent nightly build.