Hello, I would like to announce that the relay that we use for IaMP and SWR Caster now supports MBCaster as well. A quick explanation: relay is option 7, which allows you both parties who are unable to directly connect to each other to initiate a connection via a third party and then tunnel through to each other. This is not like Hamachi, where data is sent through someone else; you are still ultimately directly connecting, but using a host to initate the connection.
To use the relay, first make sure neither side can host (if either side can it's easier to just use option 2). Both parties should select option 7, enter port 7500 UDP, and then this IP: 209.237.242.30, which is the server where the relay is hosted. You should see the prompts "Now waiting for introduction" and "now waiting for response", and it will connect as normal if successful. If you time out with the relay then you may need to resort to Hamachi or figure out how to port forward properly. In order to facilitate spectating, MB Caster will print out the IP and port that you are connected on for you to copy and paste to other people once you are connected. Hope this helps.