Doesn't Arm look for 9051?
By default, but it can be any port you edit into the rc.
Apologies for the rudimentary question but did you try 'arm --interface 9051'? I assume by 'edit into the rc' that you've changed the default via the armrc but if I was in your shoes I'd give the interface argument a quick try. Also, you can try running 'arm --debug' to possibly get a little more information.
Cheers! -Damian