Having spent days trying to get the Sagepay integration kit to work on a server within our campus via a port forward I realised two things:-
a) Sagepay test servers won't find you with a port appended to the url - you need something like grok which totally rocks (lets a port out via a tunnel to a temporary fqdn which you use in the provided lib/config.php file)
b) The notificationURL pointed to file is not actually included in the kit - you have to write yourself a small file that just echoes the small allowed data set as per last para in red bottom of p29 in the v3 server integration doc from sagepay. I had seen that para and ignored it all week and gone grey(er) in the process.
Now this may be obvious to the veterans but it foxed me - so hope this helps a bit.
I'm now notifying proper data happily on my local server - and even stepping through notification php files with netbeans.
Just need to dig my way through omnipay - which appears to be a challenge with Sagepay and I'll be running happily.
Only took me a week !
cheers
Martin