Design and implementation of a distributed X-multiplexor

Abstract

Application sharing is an important aspect of collaborative computing. One mechanism for sharing applications is a multiplexor, a tool that broadcasts input/output messages from a single client to multiple displays. We describe the design and implementation of a multiplexor for X windows that supports a heterogeneous environment and works effectively across both local and wide area networks. This X-multiplexor is composed of two distinct components, the Collaborative Computing Frameworks X-Multiplexor (CCFX) which acts as a pseudo server for the client, and the Collaborative Computing Session Manager (CCSM) which renders the client images and supplies the user interface to the system. In effect, CCSM acts as a distributed window manager, ensuring that all participants have the same view of the shared clients. This two headed approach offers significant gains in flexibility and resource usage. CCFX and CCSM can communicate using any reliable transport protocol. This can result in significant reduction of bandwidth, decreased latency, and avoids some TCP/IP communication required by the X protocol. In addition, this architecture facilitates the creation of a virtual X environment. Using this virtual environment, instead of an actual X server's environment, and then translating the virtual properties to a specific server's properties, allows for more robust support of heterogeneous systems.