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Modbus RTU to Modbus TCP conversion
How to connect a device to the ethernet, so that it could communicate with OPC servers that support Modbus TCP format?


We developed a device which communicates via RS 232 port using Modbus RTU format. We would like this device to be connected to the ethernet, so that it could communicate with OPC servers that support Modbus TCP format. What is the easiest way to do this?

Is it possible to get some RS-232 to Ethernet converter available out in the market to do the job? If so, are there any recommendation? I would appreciate any comments or suggestions regarding this. Thanks in advance for the help!


By mark oldham on 19 February, 2004 - 6:10 pm

hi kelly

i think this is what your looking for:


By Benoit Galarneau on 19 February, 2004 - 6:23 pm

Look for Schneider TCP-IP bridge 174-CEV-300-20. They're easy to configure & use, and well documented.

You can use serial modbus OPC software e.g. from Kepware, Matrikon, etc.

By Andy Burgess on 19 February, 2004 - 9:34 pm

Schneider have a Modbus to Ethernet bridge. Part number is 174CEV30010. Search on their website for the user manual. It simply converts Modbus RTU/ASCII to Modbus TCP, it is not an OPC server. Cost is just under 500 GBP.


By Fernando Capelari on 19 February, 2004 - 9:28 pm

There any many Modbus TCP to Modbus RTU converters available in the market, from different vendors. I've personally used the one from Schneider Electric, which part number is 174CEV30020.

You should be able to find its catalog and manual at and then request a quotation at the Schneider Electric office or distributor nearest to you.

Hi Kelly

Zworld ( have a product called EM1500 (part no 101-0583), which is configurable via their EM1500 Tool kit (part no 101-0586)

Best of luck

Ben Loots

1 out of 1 members thought this post was helpful...

Hello Kelly.

I think there are a few brands of Modbus/RTU to Modbus/TCP gateways on the market. My company, HMS Industrial Networks, is one manufacturer. It is a "transparent" gateway, so it automatically routes Modbus messages between Modbus/RTU and Modbus/TCP. The only programming that you have to do is to set the IP address and the serial parameters for the RS-232 port. You can read about this at our web site:

If you have technical questions, feel free to call us at 773-404-3486 and press 5 for technical sales.

Best regards,
Trevor Lang

The device you're looking for is called a serial gateway. It will convert the ModbusRTU serial protocol to ModbusTCP/IP and back. Control Microsystems makes one ( as I'm sure do many other vendors.

Suprise, suprise! Schneider Electric makes just such a device. CEV 300 20 converts Modbus TCP-IP to Modbus and visa-versa. Contact a local distributor or one of the many web sites, such as and search the product. Stuck? Contact me via this site. Many users without issue.

By Gopesh Sanghvi on 20 February, 2004 - 7:45 pm

Hi Kelly,

The easiest way is to get the some RS-232 to Ethernet convertor.

I have tried Moxa's DE-211 convertor. It works fine.


By Jaroslaw Berezowski on 23 March, 2004 - 5:44 pm

They manufacture Modbus TCP-to-serial gateway NPort 6110 - I think the cheapest device available worldwide.

You could use bridge 174CEV30020 (Schneider Electric).

Control Microsystems makes a Class 1 Div 2 Serial ModbusRTU to ModbusTCP bridge called the 5906 Etherynet Gateway. It is also rated for use in -40 to 70 deg C.

Good luck with you project!


Like Brian said you can go with the CEV 300 20 bridge but you can probably get the same product from a third party for half the cost. Also, remember that SE requires a contract for all level 2 technical support.

Could you please list these third party brand(s)?



Thank you guys for all your input! I appreciate your comments and thanks once again.