You will have to try different servers. You will not be able to enable Ident over a Mobile connection (in most cases).
In case you want to try, you need to allow incoming TCP connections on port 113, which means configuring your phone's firewall and your computer's firewall to permit inbound connections on that port.
Mainly, try a different server until one works. Or abandon Undernet (it's dying) and try another network. I might recommend Freenode or EFNet.