Secure instant messaging (IM) and private LAN chat software for organizing effective real-time communication system over office LANs, business and corporate large networks, enterprise-size WANs and VPNs and Internet. Software products for Windows and mobile platforms include a stand-alone self-hosted IM / chat server called Bopup Communication Server, rich-featured messaging client Bopup Messenger and one-way IM pager called Bopup Observer with a set of business features including internal and s