Retroshare establish encrypted connections between you and your friends to create a network of computers, and provides various distributed services on top of it: forums, channels, chat, mail… Retroshare is fully decentralized, and designed to provide maximum security and anonymity to its users beyond direct friends. Retroshare is entirely free and open-source software. It is available on Android, Linux, MacOS and Windows. There are no hidden costs, no ads and no terms of service.
Source: Retroshare