Com口调试工具,里面有附有源码，如果有需要，可以作适当的改动。-Com debugging tool with a source inside, and if necessary, make appropriate changes.

modbus 的源代码截取。里面专门针对于com口通讯的编程可以用于初学者学习。-modbus source code interception. Inside specifically for the com port communication program can be used for beginners to learn.