I am going to working with modbus, so I have got documents from Modbus-IDA or so. Documents on serial modbus was not difficult, but documents on TCP/IP modbus was very hard to understand. Is there any prerequisite before reading these TCP/IP modbus documents? I don't know much about TCP/IP protocol, and is this why I can't understand the documents? What should I know to understand these documents? There is no much possibility I should implement TCP/IP modbus but I should be get prepared. Please answer. Thanks.