Asuming that you are asking this because in english when you are meeting someone at night you say "good evening" when you arrive and "good night" when you leave. in this case "buenas noches" can work for both cases.. I'd add some extra words for when you are leaving "que pasen buenas noches"

Claro, se puede saludar diciendo "buenas noches" aunque es un saludo formal. Personalmente nunca le diría buenas noches a un amigo simplemente le diría: Cómo estás? Espero que mi respuesta te sea de ayuda! :) saludos!

You can say Como estas bcz it doesn't matter when you're saying that it still means like how are you, Buenos noche means goodnight