Can I serve a person court papers at their work or where I know they will be?

I don't know someone's address to serve them small claims court papers. The reason is they moved from my house and I don't know where they are. My house is their last known address. Can I serve them at their place of work? and if so will the court still require them to have a physical address? The thing is they are sort of a wanderer going from place to place.