GMS client lib is an open source access library for Grid Messaging System
You will find precompiled dll binary for Windows, and the Visual Studio project. the heart of this project is the gmsbl.h which allow to build broject surround gmscl.dll/so.
The original library source is available here
The server is available on various platform, check all binaries here, and could be used as a general messaging purpose system. Please read server description for details.