You are going to have to be more clear about what device you are talking about. Is pocket wifi some brand name or a generic name for a portable router.
A ethernet port takes almost no power so you should be able to use it while you have a charge cable hooked up. It would not really be any different than if the router ran on a normal power adapter.
Now if you are doing something like using a USB ethernet and also a USB power on the same port or something then I don't know.