Bopup IM Client Software Development Kit (SDK) is a toolkit for Windows platform that provides documentation, samples and COM components for building powerful instant messaging functionality into existing applications, creating and developing a chat messenger software based a client/server architecture. Applications built on this SDK interact and communicate with Bopup Communication Server (IM server software) that must be installed as a server-side part of the instant messaging system. Bopup IM Client SDK provides functions for connecting and establishing IM session with the communication server, sending/receiving personal and group instant messages, receiving urgent and high-priority tasks from the server, managing user's contacts, receiving presence status updates within the Contact List. This SDK supports various authentication methods to authorize users on the IM server: Simple, Windows Authentication (SSPI) and using Private login and password credentials entered by a end-user. Using SDK components it is possible to implement instant messaging client applications using various programming languages and platforms including C/C++ and Microsoft VB.NET/C# frameworks. SDK library also provides an interface for VBA (Visual Basic for Applications) environment support that is available as built-in development platform in Microsoft Office software and allows to create macros for a range of Office applications such as Excel, Word, Outlook, Access, PowerPoint and others.