A hub would not be capable of interferring with what you want to do on port 80 (the HTTP port) or any other port. All they do is regenerate the signal and send it on. Only a router looks at IP information such at what ports are being used and could act like a firewall and either allow or not allow using that port. The built in iptables firewall in Linux could also be set allow or not allow incoming or outgoing packets being sent to port 80.
Jeff, you seemed a little unsure about what was working or not working on your network? Could you clarify what you ment? By the way, my network at home consists of two computers hooked together with just a crossover Ethernet cable and no hub. The old computer has RH8, SuSE, Slackware and DOS 6.22 on it. The new computer has RH Linux 9, RH 8, RH 7.2, PC DOS 2000, Win ME and Win 2K all on it. I have only done a few crude (but successful) experiments with sharing folders between the two with Samba and in one case using NFS instead. So far I have only used MySQL on my new computer and did not try to share anything.
I am probably at about the same stage in learning to use MySQL and not yet even tried to use any kind of midde-ware such PHP or Pearl. However, I did have a database course in the mid-1990s and we learned how to tell if a database in third normal form. We also learned to use SQL commands which were only an optional alternative way of doing things under Microsoft Access. I hope you find your MySQL class interesting!