Modbus TCP/IP at a Glance
Source: B&B Electronics
B&B Electronics discusses the Modbus TCP/IP with the use of this paper published by Simply Modbus. Transmission Control Protocol (TCP) and Internet Protocol (IP) protocol are the two transport protocols for the internet that are always used together. These TCP and IP protocols are used to send Modbus information across the internet. The data transferred is first passed to TCP protocol. Here, additional information is attached and given to IP, which then places the data in a packet or datagram. This information then further transmits to the target. As TCP is a connection-based protocol, it is essential for it to establish a connection before transferring data. The Client in Modbus TCP is called Master while the server is called Slave. The master has to establish a connection with the slave. The server waits for an incoming connection from the Client and once the connection is established, it responds to the queries from the Client until the client closes the connection. In case of Modbus TCP, the message is not sent through serial data cables. Rather, the information is wrapped and sent over a computer network.