The rcon should be fully implemented in the MCS side; it works simply - you send it a command, it executes it (as if given in the server console) and sends the results back to you. There was a rcon utility for vanilla servers that displayed things like banned players, that used to work when I last touched the rcon server. Unfortunately the documentation is somewhat vague so I didn't know whether the official rcon should work like a "tee" linux command, copying all the console output to the socket, or act like a separate channel over which commands can be sent; I've chosen the second variant, it seemed more logical to me at the time. If I were to implement it now, I'd probably choose the first variant, as that would allow the rcon management tool to even display the server's console log, even if it were a bit complicated with the output of commands possibly interlacing with other server output.
To enable rcon, you need to set these values in settings.ini:
Code:
[RCON]
Enabled=1
Password=PasswordToUse
PortsIPv4=25575
PortsIPv6=25576
Careful about the password, though, the protocol has no encryption, so it's sent over the link in plaintext. That's probably the biggest disadvantage of rcon overall; if it had been implemented over SSL, it would have been much better (because it would effectively eliminate the need to run MCS under "screen")
I guess I wasn't explicit enough with the answer about which commands are supported. The rcon supports the exactly same commands as the server console, which means any plugin can implement a command that is available for both. Actually most of the useful commands such as the banlist is already implemented in the Core plugin.