Thanks. So it would need whatever the outside IP of my laptop is, not a static IP I could configure?
No, it needs to be the inside address.
On windows, you can click on the network in the system tray and do "Properties", scroll down to the bottom of that and look for the IPV4 address.
If the venue is one you use often and you have control over that DHCP server OR you know that there is a range of static addresses you could use there then you could fix the address. If not, you'll need to check it each time.
Optionally you can go into the laptop MC and force it to update the addresses for the access key by doing "test server" under Options->Media Network. If you do so you'll want to do that again when you get back home.
MC will do that automatically in the background every so often, you are just making it do that faster.
Also if your venue has an outgoing proxy server with restricted ports MC might not be able to do that update in either case so your only option would be to use the IP address as I outlined above.