Help with firewall port opening

Question

I'm a newbie at this, so please be patient. And my Time Capsule is less than a week old, so I'm still in the learning stages.
I purchased an iPod Touch and one of the programs from the App Store--Pocketpedia--requires certain ports to be open in order to sync with my Mac pedia programs.
I went into the Time Capsule>Advanced settings to try to open the appropriate 2 ports (one for the Powerbook and one for the Touch). I'm obviously doing something wrong. That wouldn't be heard since all of the terminology is foreign to me. I know that I need to open the two TCP ports.
I clicked on the + to add a new service/port. I wasn't sure if I needed the numbers in Public TCP ports or private, so entered them in both with the numbers separated by commas.
I thought that this would be "personal file sharing" so I tried to choose that under "Service". However, when I did that it said "A pulic TCP port number conflicts with a file sharing port on the base station. Disable file sharing or choose a different port number." Actually, once I choose "personal file sharing", it autofills in port 548 into the two TCP numbers. That's one that's opened within System Preferences. So it actually won't let me change that number at all. When I try to, it services menu defaults back to "choose a service".
Needless to say, I'm very confused. I did go ahead and create a service with the two port #'s and without designating it a specific "service", but that doesn't seem to fix my problem with allowing the Touch to sync with my Powerbook.
Any help would be much appreciated.

Answer 1

With port mapping (forwarding) you "open" ports on the router's firewall in order to allow Internet traffic to reach a host device on your local area network (LAN). In this case your iPod Touch and PowerBook. However, you can only map the same port(s) to only one device. For example, you cannot map port 548 to both the Touch AND the PowerBook, only one or the other.
The typical port mapping setup requires two basic steps:
1. Assign either a static IP address or reserve a DHCP-assigned IP address to the host device.
2. Map the appropriate port(s) on the router to this host device.
The following is a more detailed list of steps ...
To setup port mapping on the Time Capsule (TC), either connect to the TC's wireless network or temporarily connect directly, using an Ethernet cable, to one of the LAN port of the TC, and then use the AirPort Utility, in Manual Setup, to make these settings:
1. Reserve a DHCP-provided IP address for the host device.
Internet > DHCP tab
o On the DHCP tab, click the "+" (Add) button to enter DHCP Reservations.
o Description: <enter the desired description of the host device>
o Reserve address by: MAC Address
o Click Continue.
o MAC Address: <enter the MAC (what Apple calls Ethernet ID if you are using wired or AirPort ID if wireless) hardware address of the host computer>
o IPv4 Address: <enter the desired IP address>
o Click Done.
2. Setup Port Mapping on the AEBSn.
Advanced > Port Mapping tab
o Click the "+" (Add) button
o Service: <choose the appropriate service from the Service pop-up menu>
o Public UDP Port(s): <enter the appropriate UDP port values>
o Public TCP Port(s): <enter the appropriate TCP port values>
o Private IP Address: <enter the IP address of the host server>
o Private UDP Port(s): <enter the same as Public UDP Ports or your choice>
o Private TCP Port(s): <enter the same as Public TCP Ports or your choice>
o Click "Continue"
(ref: "Well Known" TCP and UDP ports used by Apple software products)