Cyber-physical internet: gateway protocol algorithm for smart port operations with sea-rail multimodality

With the rapid development of global logistics, the role of smart ports in optimizing sea-rail intermodal transport is becoming increasingly prominent. However, the lack of unified information sharing and real-time coordination mechanisms between heterogeneous transport networks has become the main bottleneck in improving efficiency. This paper proposes a distributed decision-making framework based on the Cyber-Physical Internet (CPI) to address the key issues in smart port operations involving sea-rail multimodality. A five-layer CPI architecture, inspired by the TCP/IP model, is developed to standardize information exchange and operational processes. Departing from the conventional ship → yard → train workflow, we investigate a novel sea–rail coordination strategy wherein trains serve as mobile temporary storage yards. This setup facilitates direct ship‑to‑train transshipment. A mathematical model and a tailored CPI gateway protocol (CPIGP) algorithm are developed to optimize container allocation, maximize train loading rates, minimize storage yard usage, and reduce operational costs. Through extensive case studies within the CPI five-layer framework, spanning both small-scale and large-scale scenarios, our CPIGP algorithm demonstrates superior performance over exact, non-black-box baselines, including fixed-rule manual and dynamic programming methods. The advantage is particularly apparent in greater efficiency and resilience under complex operating conditions. Collectively, the work advances intelligent, sustainable, and adaptive smart port operations through distributed, CPI-enabled decision-making.