PLC communication over a modem

Hi Guys,

Need a little help! I am trying to communicate with a compactlogix controller over a modem from my PC. The PLC is connected to a modem and on the other side my PC is connected to a different modem. Basically, I am trying to create a wireless communication.

This is my first project over a wireless communication. I have managed to do the port mapping on the PLC side and when I type the IP address, in my PC browser, for the modem which is connected to the PLC, it will take me to the controller web page. This means I can able to access the PLC from the internet explorer of my PC.

However, I cannot go online or I do not know how to go online with the PLC (RSLinx).

I would appreciate any suggestion.

Thank you

What brand and model of radio modems are you using ?

Because you can access the CompactLogix embedded web page over this wireless link, it suggests that basic TCP/IP connectivity is working.

ControlLogix uses TCP Port 44818 for communications with computers. Are there any firewall or other applications that might block that TCP port ? You may wish to run the Rockwell Automation Windows Firewall Configuration Utility.

The free utility TCPing can help you make sure that you can connect to TCP Port 44818 on the controller.

If you are using the EtherNet/IP driver in RSLinx Classic, you may wish to try instead the Ethernet Devices driver.

Dear Ken,

Thank you for the reply, I am using a modem router from a local Internet service provider.

Currently I have no firewalls turned ON on my PC and I have also tried running Rockwell windows firewall utility. However, I do not understand where and how to use "TCPing' utility. I tried to use it in command prompt but it doesn't recognize.

Thank you.

TCPing isn't a built-in Windows utility; you need to download it here: LINK

Are you running WiFi on your computer and connecting the CompactLogix to a modem/WiFi Access Point device ? Please explain this in detail, as it is not clear in your post.

It's very likely that the "modem" is behaving like a router and will not pass broadcast packets. The "EtherNet/IP" driver in RSLinx Classic depends on broadcast packets, while the "Ethernet Devices" driver requires you to enter the target IP address of the controller manually.