Quote from jman650
check to make sure that you give him the outer IP, not the one you use.
go there to find your actual IP.
Then, make sure you're doing the :25565, and that you opened that port.
Quote from Lord_Ralex
Just going out on a limb: Any mods with the clients? And have you tried to force update and see the cause?
Quote from rchI use my shoe temporary Minecraft window sponge.