For year's I've used Back to My Mac (BTMM) and Screen Sharing to help my mother with her iMac. It worked dependably until a few months ago, I think around May. Now, her machine no longer appears in the "Shared" category that appears on the left side of a Finder window.
I've done quite a bit of troubleshooting (http://support.apple.com/kb/HT4907) but still haven't solved the problem.
The Apple Support article OS X: Using and troubleshooting Back to My Mac with your iCloud account mentions..
Ensure TCP port 5354 and UDP ports 4500 and 5353 are open on your firewall.
...but I'm not sure how to "ensure," let alone check to see if these ports are open. Any advice on checking/managing ports?
From my Mac, I tried using the "Port Scan" function of Network Utility. I entered her IP address and scanned specific port ranges. I verified a few "common" ports by scanning the range 20 to 25 (21 & 22 are open, as expected) but when I scanned for the ports listed above, they did not seem to be open, i.e., the output was...
Port Scan has started…
Port Scanning host: [my.moms.ip.address]
Port Scan has completed…
Here's some background info...
- My mom and I are both using OS X 10.8.
- My mom's iMac is connented to a cable modem via ethernet (no wireless router).
- My mom's Internet provider is Charter.
- My MacBook Pro is connected to a cable modem via WiFi (TimeCapsule).
- Neither of us are using a Firewall.
- Both of us have Screen Sharing and File Sharing on.
- BTMM works fine between my other Macs.
- My other Macs don't show up as "Shared" items on my Mom's iMac.
- I've serached in Keychain Access for old .Mac and MobileMe keychain items to delete but found none.
- I tried the command "netstat en1" from Terminal but I don't understand the response.
- I've tried running ShareTool 2 in demo mode: Screen Sharing works perfectly but I'd like to get iCloud's BTMM to work the way it's intended to for free.