Blockchain solves the problem of loss of data control and the single point of failure faced by centralized content platforms. Despite the huge potential, existing blockchain-based data trading solutions still suffer from major issues, such as data privacy breaches, difficulty in ensuring fairness among participants, significant resource consumption due to interaction with the chain, and computational consumption during the file preprocessing phase. To fill the gap, this paper introduces PDTS (short for practical data trading scheme), an innovative enhancement of the fairswap protocol that utilizes state channels and Proof of Delivery. Our scheme is specifically designed to facilitate efficient data trading between entities dealing with large data volumes. We provide a formal security analysis and developed a prototype to rigorously evaluate the effectiveness of PDTS. Experimental results demonstrate that our scheme not only significantly reduces resource consumption but also maintains high system availability, thereby offering a robust solution that addresses the key drawbacks of current blockchain-based data trading frameworks and significantly enhances trading efficiency and security.