Roslaunch using different port?

edit

I'm attempting to use roslaunch to start nodes on 2 different machines. Apparently roslaunch will create it's own ssh connection - I have my network configured so that I use public / private keys for authentication, but I've set the ssh to be done over a different port. How would I configure my roslaunch file to do the same? (i.e. port 42 instead of 22)

Current file:

<launch>
  <machine name="bbb" address="bbb -p 4242" user="sparky"/>
  <machine name="spearmint" address="localhost" default="true" />
  ....
</launch>

Obviously that's the wrong syntax, but that's what I'm trying to achieve.

For reference, I can run ssh sparky@bbb -p 4242 and connect just fine.