Openfire - Openfire (formerly Wildfire) is a cross-platform instant messaging (IM) and groupchat server.
Dialog Messenger - handy and feature-rich enterprise multi-device messenger available for server or cloud – Slack-like, but not Slack-limited
Bopup Communication Server - Secure instant messaging (IM) and private LAN chat solutions for organizing effective real-time communication system over office LANs, business and corporate large networks, or enterprise-size WANs and VPNs
Ripcord - A desktop chat client for Discord and Slack
ejabberd SaaS - Realtime XMPP and MQTT Software and Infrastructure as a Service.
Done Hui - No need to switch between multiple pieces of software to get through the workday. CHATS: Communicate freely. CALENDAR: Know your team's availability, plan meetings. No more conflicts. TO-DOs: Stay on top of all projects. FILES: All files, one spot.