Unable to start web interface

[RuleRulez]

See attachment. It is working on my MacBook, and also under another user on my iMac, but not under my own account. Ruby seems to work.

Anybody a hint?

[RuleRulez]

I found out that WeBrick is already using port 11872.
If I start up Ruby via the Terminal with 'server -p 11870' it works.

How can I set in OF the port to a different one than 11872?

Or how can I find out which program is using port 11872?