Without seeing the actual configuration there isn't enough information to make a decision. Am I seeing the port side aspect of of the vessel? A port side running light at 112.5 degrees and a masthead light at 225 degrees? Where are the lights in relation to each other?
When boating at night, a single white light on a vessel tells you that it is anchored.
If you see a single white light directly ahead at night then you are the give way vessel.
When boating at night a red and white light on a vessel tells you that you must give way to the other vessel.
fishing at night
A commercial vessel towing at night displays a white towing light above the stern of the towing vessel and a second white light at the stern of the tow. Additionally, the vessel should show a green light on the starboard side and a red light on the port side, as well as an all-round white light at the stern of the vessel being towed. These lights help indicate the vessel's activity and ensure safe navigation for other vessels.
It depends on its relative bearing and also its proximity.
You are boating at night you see a single white light directly ahead, you should give way by going around the other vessel.
you are on the port side of the vessel
You are the stand-on vessel but should take precautions in case the other operator doesn't see you.
A white light is the color of light that must be displayed on a vessel towing at night, I t must be displayed at 8.2 feet higher than the colored sidelights. It should have an all round white light visible for 2 miles.
another vessel is at anchor
The green light would be the starboard steaming light, the white the masthead light. What you would do would depend on factors such as its releative bearing and in what waters you are sailing.