C2CFTP: Direct and Indirect File Transfer Protocols Between Clients in Client-Server Architecture

In this paper, we propose an efficient direct and indirect file transfer protocol (C2CFTP) that transfers files between clients in a client-server system. Existing file transfer methods use an indirect transfer method through a server to transfer files between sending and receiving clients or a direct transfer method that connects a direct data channel between clients. However, in the case of indirect transmission, unnecessary file input/output (I/O) is required by the server, and in the case of direct transmission, a problem arises in that the file transmission delay time is increased due to channel management cost. The proposed C2CFTP can omit unnecessary file I/O overhead by relaying the file to the receiving client instead of storing the file at the server for indirect transmission. For direct transmission, instead of connecting a data channel every time a file is transmitted, the channel connection overhead is reduced while minimizing the waste of the number of direct channels between clients by maintaining the first connected channel while the file transfer is required within a predetermined time. File transfer experiments show that the proposed file transfer protocol has a reduced file transfer delay time than the existing methods. In addition, it was confirmed that the direct transfer method is suitable for transferring large files, and the indirect transfer method is suitable for transferring multiple small-sized files in a bundle.