In this 5–10 minute guide, you will set up communication with a Modbus TCP device and create several tags available for the OPC UA client. If you do not have Monokot Server, go to this section to download and install it.

Connection to Monokot Server

  1. Open Monokot Server Administrator

  2. Create a new connection or just click the Connect button to connect to the local server

  3. Please wait until the main application window opens

Configuring Modbus TCP Device

  1. In the Server Explorer pane, double-click on Devices to open the device manager

  1. In the device manager, click on the New Device button

  2. In the drop-down menu, select Modbus TCP

  3. On the settings pane, enter the IP address of the target device and slave ID (if required)

Creating Tags

  1. In the Server Explorer pane, double-click on Tags to open the tags manager

  1. In the tags manager, click on the New Group button

  2. Double-click on the new group, name it as MyModbusTags and press the Enter key

  3. Click on the New Tag button

  4. To associate the tag with a device, double-click on the Device cell

  5. Click on the ... button in the device cell

  6. In the device selector dialog window, select the Device1 and click the OK button

  7. Double-click on the Address cell

  8. To specify Modbus register, in the address editor, type 300000@WORD and press the Enter key or use graphical address editor by clicking on the Pen button. Thus, the tag will be addressed to the first register of the Internal Registers area in the Word format

  9. Click on the New Tag button and associate the created Tag2 with Device1

  10. Set address 400001.3 to Tag2. Thus, the tag will be addressed to the fourth bit of the second register from the Holding Registers area

  11. To make your changes take effect, click on the Sync button (on the top panel) or press the F5 key

After the changes are synchronized with the server, the Tag1 and Tag2 will be associated with the specified registers and will become available to the OPC UA client.

Testing by Third-party OPC UA client

In the OPC UA client, connect to the Monokot Server using the following endpoint parameters:

  • Endpoint URL - opc.tcp://localhost:43043/MonokotOPC

  • Security Policy - None

  • Authentication Mode - Anonymous

Now you can see the created tags and device in the object browser of your OPC UA client.

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