Modbus TCP Data Transmissions

Messaging is supported in both peer-to-peer and Client/Server configured networks. In both cases object messages are communicated serially in the “data” portion of the Modbus protocol of each message transaction
All object messages are sent between two nodes to execute service transactions. All service transactions are associated with “request” services and consist of a request message and a corresponding response message.
Since both clients and servers may be constructed using devices which support only the alternate transport function codes, it is necessary that client and server devices support the alternate transport mechanism in addition to the object messaging function code if so supported.