The main differences between Modbus TCP and Modbus RTU are their communication mode, data transmission mode, data format, reliability, network topology and verification mechanism. 1   Communication mode: Modbus RTU (Remote Terminal Unit) uses asynchronous serial transmission and can communicate through various media (such as wired RS-232/422/485, optical fiber, wireless, etc.), which is suitable for point-to-point or multi-point-to-point topology. Modbus TCP is based on Ethernet communication and uses TCP/IP protocol. It is suitable for star or bus network topology. The device is connected to the master station through an Ethernet switch or router.   Data transmission mode: Modbus RTU transmits data directly through binary data, while Modbus TCP converts each byte of binary data into a fixed two-bit hexadecimal string, and then concatenates them in sequence to transmit data in the form of TCP code.   Data format: The data format of Modbus RTU includes fields such as start character, slave address, function code, data, and error detection. The data format of Modbus TCP is TCP/IP data packet, which contains fields such as source IP address, destination IP address, TCP port number, Modbus application data unit (ADU), etc.   Reliability: Modbus RTU uses differential signal transmission at the physical layer, has good anti-interference ability, and is suitable for industrial environment. Modbus TCP uses the reliability mechanism of TCP/IP to retransmit data packets, and has high requirements for the network environment.   Verification mechanism: Modbus RTU performs CRC16 verification on the sent and received messages during the transmission process to ensure that there are no errors or damage to the data during the transmission process. Modbus TCP does not have verification when sending, but does verification at the transport layer.   In summary, Modbus RTU is more suitable for industrial field environments, with shorter transmission distances and stronger anti-interference ability; while Modbus TCP is suitable for local area network or wide area network environments, with longer transmission distances, but with higher requirements for the network environment.   As room thermostat manufacturer, E-Top provide widely range of Modbus RTU thermostat. If Modbus TCP need, we can accept OEM/ODM development.