Taking rail transportation industry as the background, a framework of the "Internet of Things" for Smart Rail Transportation (SRT-IoT) was proposed and its key techniques were explored. With the perception of the next generation Internet, this framework was characterized by a Backbone Communication Network for SRT (SRT-BCN) interconnected by various Basic Access-Resource Networks (BARN) with clients and resource servers. Furthermore, rail-transportation specific BARNs were classified into two groups: Train-based Access-Resource Network (TARN) and Ground-based Access-Resource Network (GARN). Techniques feasible for different network were also analyzed in different details, and an emphasis had been given to TARN with a conclusion that TARN related network technologies should further develop as a research basis of SRT-IoT for wider interconnection.