RS232 / 422 / 485-eth module is a composite serial port server. It not only has the function of conventional serial port server, but also can convert the standard RS232 / 422 / 485 serial port signal into TCP / IP signal, and realize the two-way transparent data transmission between RS232 / 422 / 485 serial port and TCP / IP network interface. At the same time, it has the function of Modbus gateway, realizes the conversion between Modbus TCP and Modbus RTU protocol, makes the serial port equipment have the function of TCP / IP network interface, and connects the local area network for data communication. It can greatly reduce the wiring engineering of serial port equipment, easy to maintain, and expand the communication mode and distance.