While there are different things that can happen to a port and various types of “haze”, the first line of defense that we would recommend is hot water and soap.
Quite often a port would have blotches on it from several years of letting it dry with salt water and not rinsing it off and drying it completely right away.
In those cases, we suggest trying vinegar, alcohol and water with a microfiber cloth. This takes some time but usually eliminates any residue left on the port.
If even that doesn’t cut it, it may be scratched. In that case, you can use the Novus Polish set for acrylic ports, at your own risk. If not used properly it will likely render the port unusable, so please use with care.