MBU - PC Multiplayer Setup Howto (Works As Of Version 1.8 )
Marble Blast Ultra PC Port from http://marbleblastultra.tk requires additional setup for multi player because the creator of the MP match needs to be port forwarded, so here's a tutorial on how to do port forwarding. This how-to does not use Hamachi, Tuungle or BitTorrent/uTorrent/another torrent, and does not require a router password. Instead this tut uses the method of uPnP to portforward and host the server. These easy steps in this tutorial will make portforwarding for MultiPlayer much less convoluted. I will soon add captions so that people with other languages will understand.
Albertino Port Mapper: http://www.geogensoft.com/software/10-port-mapper
Mirror Link: https://mega.nz/#!IogXRSAS!rholcfDxSnDoR0wsag8TwIerHNip1DBkCytbM9uDLzk
[As of 2015-10-07 the site seems to have been reported as an unwanted software site, but the website still seems the same as before]
[As of 2015-10-25 many users have reported the site is down, so I've reuploaded the file to MEGA]