I am not familiar with GENI. But if you are accessing the server via a non standard SSL port (EG: Anything other than say TCP port 443) then you would need to specify the exact port you are using. If there is no web UI, then I am unsure what port you will be using for connection (outside of SSH). Although here is a chef document that defines what the standard ports that are used in a chef deployment.
Here is an example of my knife.rb file (with obfuscated data of course) that has a successful connection back to our chef server that is using the standard web SSL port (443). As it is standard, I do not need to specify the port.
current_dir = File.dirname(FILE)