Trying to set up LAN

I have been trying to set up my kids LAN for Minecraft, but as it is now I can only host a LAN-game from one computer. The other way my firewall blocks the access. I have been trying to find a way to let it through without success. The conection that is blocked looks like this:
C:\Program Files (86)\Java\jre7\bin\javaw.exe Denied TCP and then the source IP and Target IP
How do I set access for the other computer? Happy for all help:)

Maybe I should add that I use the free version of Comodo Firewall on both computers and they are updated today.
and that Im ot so experienced at this. I hae tried to search the forum for answers befor posting this but is there a thread Ie missed please Point me to it.