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Problems connecting to v570 via ethernet

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  • MVP 2023

I love Unitronics PLCs, but I am constantly having a problem getting my laptop to connect to a v570 via ethernet. It always fails to connect the first time and I usually putz around with it for a few days and finally get it to work, after much lost time. Here is my situation:

Using WinXP on the laptop and VisiLogic 8.6.3 (I know this isn't the latest version, but I am often working with installed systems and I want to maintain continuity).

I can connect every time with a serial cable.

I can ping the PLC every time.

I assign a PLC name & port number and confirm them in the communications settings.

As far as I know, these are the things I need to be able to communicate via ethernet:

PLC IP address

PLC name

PLC port number

Compatible, non-conflicting IP address assigned to the laptop

Crossover cable when connecting directly, or straight cable when connecting through a hub

TCP/IP card & socket initialization and PLC name in ladder using SB2

My problem is I have a PLC in the field that I will need to connect to via ethernet. Sometimes I do some updating and troubleshooting with a new PLC here in my office. I open the box, install the ethernet card, confirm functionality of the card, and download the program with a serial cable. At this point the PLC has the assigned IP address, card & socket initialization, and PLC name, exactly like the one in the field. I remove the serial cable, change the communication setup back to TCP/IP Call, confirm that VisiLogic has the correct IP address, PLC name, and socket number that matches the PLC, and try to connect. No go - I get the Communication Driver Error box (Communication over TCP/IP could not be established due to one of the following: etc, etc)

Now I know there is nothing wrong with the ladder logic, as I have connected to a PLC with this same installed program many times before. I check the laptop IP address and the first 3 octets are the same as the PLC (I'm using 10.1.1). I can ping the PLC without error. I have the laptop wireless turned off and there are no other computers on this mini network.

This kind of thing drives me crazy - it shouldn't be this difficult. What am I missing?

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Which socket and port number are you using?

Make sure the socket is configured to TCP slave.

Review the topic "What are the steps communicate with the PLC via Ethernet?(PC to PLC)

"from FAQ.


You might face this problem due to firewall antivirus or other security programs that runs on your PC.

Try to turn off any security programs and test again.

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  • MVP 2023

Thank you, Ofir. I think I've found the problem and it is mine, not Unitronics'. If I change the IP addresses on the PLC and laptop to 192.168.1.xxx, I can connect easily. Something in my laptop is acting as a firewall and preventing connection outside the range of 192.168.1.xxx addresses. I am not actually running a firewall program on my laptop that I know of, not even the built-in Windows firewall, however, I'm having trouble tracking down the source. Anyone have a suggestion for how to proceed to troubleshoot this kind of issue on a WinXP laptop?

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