User blog comment:MaxCobar1/Servers not working?/@comment-24136443-20140217002407

http://www.youtube.com/watch?v=Z8ufCtX8Ez0

That should help if you're trying to set up a server, otherwise if its someone else's server they might just need to update the program. Also, try to make sure that they IP that is being given is correct for all parties involved. If you and a friend are playing together in one house, then the IP that will be used is the IPv4 address. Hope this helps!