Trying to use mysqlreplicate fails using same port on master and slave (no replies)

Why can't I use the same port on both the master and slave? How can I get around this bug?

mysqlreplicate --master=root:xxxxxxxx@localhost:3306 --slave=root:xxxxxxxxx@10.20.20.28:3306 --rpl-user=rpl:xxxxxxx -vvv
WARNING: Using a password on the command line interface can be insecure.
Usage: mysqlreplicate --master=root@localhost:3306 --slave=root@localhost:3310 --rpl-user=rpl:passwd

mysqlreplicate: error: The master and slave are the same host and port.