We describe the Lightweight Communications and Marshalling (LCM) library for message passing and data marshalling. The primary goal of LCM is to simplify the development of low-latency message passing systems, targeted at real-time robotics applications. LCM is comprised of several components: a data type specification language, a message passing system, logging/playback tools, and real-time analysis tools. LCM provides a platform- and language-independent type specification language. These specifications can be compiled into platform and language specific implementations, eliminating the need for users to implement marshalling code while guaranteeing run-time type safety. Messages can be transmitted between different processes using LCM's message-passing system, which implements a publish/subscribe model. LCM's implementation is notable in providing low-latency messaging and eliminating the need for a central communications "hub". This architecture makes it easy to mix simulated, recorded, and live data sources. A number of logging, playback, and traffic inspection tools simplify common development and debugging tasks. LCM is targeted at robotics and other real-time systems where low latency is critical; its messaging model permits dropping messages in order to minimize the latency of new messages. In this paper, we explain LCM's design, evaluate its performance, and describe its application to a number of autonomous land, underwater, and aerial robots.
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