As much as I love to blame problems like this on IT, chances are this one isn't theirs.
Just clarify for me, your "test" is using your residential cable or dsl service and not the connection you will be using for the offshore PLC? If so...
It's always nice to make sure you can ping the the router, but must ISPs block pinging. Another thing I have found that many "residential ISPs block is low level port numbers. I believe they do this to keep you from using computers at your home as servers that are normally accessed since your only suppose to use them to access the internet although they claim they do this for your protection. My ISP blocks ports below around 20,000, which includes the port 2222 that you are trying to access the PLC one.
Now before you go any further, what are you trying to accomplish with your test? Just a little comfort in knowing it will work once your in the middle of the ocean? What type of connection will your offshore PLC permanently have? Will it have it's own or share a connection with a bunch of other equipment? If it will have its own can you go ahead and purchase the hardware?
If this port blocking is the problem then there are ways around it but whether it is worth it or not depends on the answer to the above questions. Mainly, you must get in on a port higher then your ISP blocks. Chances are they are not blocking all incoming ports, it is more of a deterrence. Pretty much your PC will have to come out of RsLinx on port 2222, route to a higher port, go through the internet, hit the router, route back down to 2222. Hardly worth it if your just wanting comfort...
