I have a Samsung Galaxy S3 Mini running Android 4.1.2. I have a regular 3G voice & data plan with an Optus reseller in Australia. I often access the Internet from my laptop via bluetooth tethering on this phone and it works beautifully, except for one small problem.
I have several web servers that I access via SSH but I have configured the SSH servers to listen on non-standard port numbers. Although I have selected very large port numbers (ie. greater than 33,000), according to the TCP/IP standard they are valid numbers so they should work fine. Indeed, I have been happily SSH-ing to these servers for years on my wired connections at home and work, but have never been able to access them when tethering.
I have just spent several hours searching the web trying to find out if this is a carrier issue or an Android issue but found nothing useful.
[Additional Notes] The configuration is as follows: laptop is paired via Bluetooth to the phone. The phone has "Bluetooth tethering" enabled so that I can share the phone's Internet connection with the laptop. So the laptop connects to the phone, the phone connects to the Internet via 3G.