使用FTP上传和下载，用到了事件，多线程同步，内存读写，文件操作。-The use of FTP upload and download, use the event, multi thread synchronization, memory read and write, file operations.

西门子PLC S7-300 & S7-400系列TCP连接上位机程序，无需PLC端再编程，源码包含C#和VB，亲测S7-300 CPU-314C-2 PN/DP可用。(PLC connected PC via RJ45 directly and do Memory write and read)