You can message and share files inside your intranet without a server.
Secured blockchain group messaging
Graphical message and file encryption tool
UDP based desktop chatting app which supports AES-256 bit encryption.
шифрованная AES переписка во vk.com
Neutron Chat allows you to communicate in networks
Underground IM is a free Java Instant Messaging solution.
A P2P Messenger which uses JXTA. It provides secure RSA/AES end-to-end