Afaik enable debugging only deals with the phone functionality.
But, Wireshark works even for wrong urls.. first of all you see the incorrect url when your application gives it to the phone in the first place, and then if it is incorrect, you'd still see it in the Wireshark trace.. e.g. if the hostname is wrong you'd see a DNS lookup for that hostname but no response, if the machine is not responding you see a TCP setup but no response, if the path is wrong you'll see the error 500.
This is obviously easiest if you're working with an IP Communicator since you can run wireshark on the same box as the IPC.. with hardphones you just need to configure a mirror/span port on the switch to see what the phone is doing - unfortunately sometimes this is unavoidable because the IPC cannot handle certain things (e.g. the whole new features introduced with the 8.3.5 load like appId, the new streaming uris, etc.) However, an IPC version 7 is supposed to be released this year and it should finally be based on the same code as the phones so apps should behave pretty much like on hardphones which will make the IPC more useful for debugging purposes.
