Modbus to TCP/IP

Figure 1 depicts several ways in which WinTECH Software utilities may be used to integrate modbus equipment with a PC network.

1. Shows a direct serial connection between the PC and the modbus, (ModScan32, ModSim32).
2. Shows a network connection from the PC directly to an interface card installed in the modbus devices, (ModScan32).
3. Shows a network connection from PC to PC. In this case the second PC acts as a bridge device between the connected modbus slave and the network, (MNetSvr).
4. Shows a modem connection between the PC and a modbus device, (ModScan32).
5. Functionally equivalent to connection #3, this depicts the built-in dial-up networking support available with Win32 systems, (ModScan32).
6. Shows a PC "Listening" to an active modbus session, distributing data across the network, (MNetMon).

MNetSvr is a Windows application which serves as a bridge between a serial modbus network and the TCP/IP protocol. MNetSvr operates according to the modbus/TCP standard, interfacing multiple network client applications with one or more serial modbus devices. Using MNetSvr to control serial data interaction with the modbus allows any modbus/TCP compatible client application running on the LAN to access and/or modify data points in the slave. Each network client operates as though it is connected directly to the device, greatly simplifying the task of acquiring data.

Whereas MNetSvr requires that the slave network be connected directly to the PC operating as the server, MNetMon is a Windows application designed to monitor an active modbus communications link, duplicating data from the slave device and making it available to other network clients. MNetMon operates transparently, listening to both sides of an RS-232 serial conversation without interfering with the existing devices. As the modbus slave transmits a response to master queries, MNetMon captures the data and maintains its own local database for operation as an modbus/TCP network server.