Chatbox is described as 'lets Dropbox users discuss shared folders and files, you can comment on each file and trace conversations,receive desktop notification for new messages, etc' and is an app in the Network & Admin category. There are three alternatives to Chatbox for Android, iPhone and Online / Web-based. The best alternative is Intercom. It's not free, so if you're looking for a free alternative, you could try Brice.
Intercom shows you who is using your product (the user's region, browser, local time etc.) and makes it easy to personally communicate with them through targeted, behavior-driven email and in-app messages.