Belkin Router Firewall Settings - Need Help Please

Question

Hi
I'm new to Apple and love the machine, but I am having a problem with the firewall on my router. Let me explain the setup, then the problem...
I have the following in my home network:
1 hp desktop running Windows XP Media Center Edition, SP3 (Professional)
1 Belkin wired / wireless router
1 Canon Pixma MP500 Printer set for Sharing (Connected to hp desktop through USB)
1 iMac 20" running Leopard OS
The hp desktop and the iMac are both hardwired to the router. The router's security settings are as follows:
Will NOT broadcast the SSID
Mac Filtering is ENABLED (iMac MAC address is included in list of allowed connections)
WPA-PSK Security ENABLED
Wireless connectivity is ENABLED (For Wii, PSP, and Xbox 360)
Now the problem...
Everything on the network works beautifully, except the iMac. It will not allow iChat services, will not allow sharing of the desktop with other iChat members. It does, however, connect to the internet, but will not access the hp shared folders or printer. When I attempt to even add the printer, the printer does not even show up. I DO have Bonjour installed on the hp, but when I run Bonjour, I get a message that reads something like, "There are no Bonjour enabled printers available."
I know it is the firewall built into the Belkin router because I placed the iMac into the Demilitarized Zone, and everything started working as expected. For those of you not familiar with DMZ on the router, it basically allows you to pick an IP address to place outside of the firewall, so you can keep the router firewall enabled, but you can choose an IP address (i.e., a computer) that is not behind the firewall.
After placing the iMac in the DMZ, I went to add the shared printer on iMac. Not only did it show up immediately and give me the ability to add it and print to it, but I could also browse shared folders on my hp. I was also able to connect to a friend on iChat, and we were able to share each other's desktops.
Before placing the iMac in the DMZ, I opened a couple of ports (I don't recall which ones at the moment), and I was able to get iChat AV to work properly, but could not get the shared desktop feature to work. I believe if I had a comprehensive list of ports to enable, I could get this issue resolved, but I can't seem to find such a list anywhere on Apple's web site (or any other web site for that matter). Do any of you have such a list of ports??
I can provide more information if needed, but any help on this matter would be greatly appreciated.
Thanks a lot in advance for your help.

Answer 1

Thank you, Larry.
I found a soft copy of the Belkin router's setup instructions on-line. I am going to enable the UPnP feature, as the manual indicates that it is necessary to have this feature enabled to do the things I want to do. The manual also indicates that the router ships with this feature disabled by default. I have not had a need to enable the feature when I had two PCs, so hopefully this will solve the problem.
In either case, thanks for directing me to the common ports. If enabling the UPnP feature does not work, at least I can see which ports I need to enable.