AppWarp cloud doesn't allow for such customizations. I believe only in some offices the IT team will block outgoing traffic on ports other than 80. Mostly firewalls are geared towards protecting machines from incoming traffic. Do you expect a significant % of users in this kind of a setup? Is your app a productivity app targeting businesses?
The other option you have is to use AppWarp S2 (
http://appwarps2.shephertz.com/). This is authoritative server that you can host yourself and modify the default listen port. The client usage is almost the same as AppWarp cloud as the server is based on what powers our cloud solution.
We also offer hosting of this on to our PaaS (App42Paas) offering -
http://app42paas.shephertz.com/dev-center/gpaas/ on which we can customize the ports for you if required.