Abstract
A local area network (LAN) for a plant factory was designed. In this LAN, three types of computers, an AT computer (AI), a workstation (WS) and a terminal computer (TC) were connected by Ethernet.
The file transfer speeds between the computers by using FTP command were examined as the following 4 conditions; (1) TC was used as a client and WS was used as a server, (2) WS was used as a client and AT was used as a server, (3) AT was used as a client and WS was used as a server and (4) TC was used as a client and AT was used as a server. The file transfer speed was the fastest in the condition (1), and the slowest in the condition (3) .
Furthermore, other two data acquisition commands in addition to FTP command were used in order to characterize the condition (1) . The two commands were COPY command in Network File System (NFS) and ONE LINE COPY command in NFS. A file transfer speed from TC to WS was the highest when FTP command was sent. A file transfer speed from WS to TC was the highest when COPY command in NFS was sent.
The effect of the file size on the file transfer speed in the condition (1) was tested by using the following three file sizes; 768, 000 bytes, 384, 000 bytes and 96, 000 bytes. File transfer speed was the same when COPY command and ONE LINE COPY command in NFS were used, i.e. independent on the size of files. However, when FTP command was used, larger size files were transferred faster than smaller size files. Thus, it was found that large file sizes such as image data could be transferred most effectively between computers by using FTP command.
