MODBUS TCP Access Remotely Over Internet


Thread Starter


In my site, I have several power meters using modbus serial then connnect each other by daisy chain method. convert to modbus ethernet. From this point i can read all of parameters by connected to etn port of my PC (Installed HMI with all modbus drivers).

In this case I want to read all of parameter remotely by internet where ever I go using my PC.

I have internet provider with dynamic IP in my site.

Please let me know steps in detail to get it.

Thanks in advance

Lynn August Linse

> ... power meters using modbus serial
> ... convert to modbus ethernet
> ... dynamic IP in my site.

You didn't say which country you live in, which can a huge impact on your options. If you are talking about 1 site, then cost isn't likely as important. If you have 1000 sites, you might want to consider putting intelligence at each site to push only 'interesting' data up over cellular, instead of blindly polling from the host even when nothing of importance has occurred at site. People who poll modbus centrally perhaps need to budget from us$10 to $60 per month, while those with local intelligence can get the cost under us$5, and I've seen it down to us $0.47 per site with 10,000 plus sites and highly tuned upload limits.

Very likely you can buy a 'cellular gateway' which includes support for the Modbus/TCP to serial RTU conversion, plus includes DDNS (or dynamic IP for DNS) updating. With cellular, dynamic IP tend to change many times each day - in fact, every time the cellular device loses & re-establishes the cellular link, so I've seen it change up to 20 times a day. This means you'll need to reference each site with a DDNS name and pay some DDNS company to help you, such as such as (used to be, which is the service I use myself).

The Digi Connect WAN family does all of the above, but so will many others.

You should probably avoid GPRS in the USA, as even today bandwidth has been dropped rapidly, and AT&T has announced it being phased out & completely gone by 2016. Given GPRS makes horrible use of radio-bandwidth, I have to assume other carriers will follow suit and cripple or eliminate GPRS to get better user/data/$$$ from fewer radio frequencies.