In the web UI for the Pi image there is a typo in the SSH info tooltip. It says to use ssh root@host -P22222 to access the server. While I personally feel that the options should precede the destination (as is stated in its man page), the option to specify a specific port is -p, not -P.
I feel that the tooltip ought to read ssh -p22222 root@host instead. (Or at least fix the option.)