The ports and network compatibility can be tricky at points, but luckily enough we have some support pages with information on them to help with the situation. These have helped me out more than once, so I hope they do the same for you!
Also, I do know that ports 5001, 5002, 8080 and 443 are acceptable by the Slingbox.
Hope this helps,
The Slingbox Moderation Team