Abstract: Time-Sensitive Networking (TSN) has emerged as a primary choice for communication in distributed real-time systems such as industrial automation, avionics, and automotive applications. TSN traffic planning aims to allocate conflict-free transmission times for time-sensitive frames while managing constraints related to network topology, resources, device capabilities, and stream requirements. The traffic planning problem is NP-complete. There is a need of quick development of open-source traffic planning software for both academia and industry. Our paper introduces LOCAP, an architecture for TSN planning with interfaces named Minimum Collection of Planning and General Table of Planning. LOCAP separates planning algorithms and tools, as well as planning software and hardware details. Based on LOCAP, we implemented an open-source TSN planner called OpenPlanner. OpenPlanner integrates multiple algorithms that leverage satisfiability modulo theories and heuristics to solve planning problems. We evaluate the runtime and solution quality of various algorithms using OpenPlanner, highlighting the need for diverse planning algorithms in different TSN applications. To the best of our knowledge, OpenPlanner is the first open-source TSN planner. Its planning results have been deployed on multiple hardware platforms, including OpenTSN, Yinhe Hengxin TSN chip, and XZ-TTE. It has been applied in various systems such as satellites, unmanned vehicles, and artillery.