Minecraft 1.7.4 LAN world not working?

I run the server, we're definitely both on the same network, we've tried direct connecting and that didn't work either. We've made sure we both have the latest update on minecraft, and it's still not working. Also I saw some stuff about checking java is allowed through the firewall, I've done that on my computer but on my brother's computer I can't see java on the list of things to allow through (it's definitely installed though). Anyone got any fixes?