MODBUS TCP issue

[mont222]

Let me make the question shorter: Does the Unitronics v570 controller (Slave, Modbus TCP/IP, Socket 3 default) support connection/communication/data exchange with two “Modbus Masters” over the same Socket (IP-address, Port: 502) simultaneously?

If yes, what should I do to implement this?

I ask because many other controllers we use support this.

[Joe Tauser]

53 minutes ago, mont222 said:

I ask because many other controllers we use support this.

Yes, you've made that clear.  I am curious if other controllers allow you to control socket assignment.

A socket can only have one connection at a time.  So the short answer to your question is no.

I've never tried to assign the same port to two sockets, but it's worth a go.  Try putting a Socket Init block in for Socket 0 and set it up as a Modbus TCP Slave using port 502.  You'll have to put another Modbus Config block in to support a second SCAN_EX block.

I've attached a program demonstrating this.  I have no idea if it will work for what you're trying to do.

The forum is not Official Unitronics Support.  You can also pose your question to support@unitronics.com. 

Joe T.

Dual Slave V570 Test.vlp

[mont222]

Thanks a lot. I'll try if Visilogic doesn't complain. I also requested support and am waiting.

[mont222]

Official Unitronics Support offers the same solution, but also says that it has not tried it.

I'll try and let you know.

[mont222]

I tried it on one controller. I set port: 502 to socket 0, socket 2, socket 3 and enabled Modbus TCP on them. !!!Success!!!

Two servers connected to the PLC, as well as another “Modscan” at the same time.

Thanks for the advice!!!

Sorry for the English, I used Google Translate

[Fernando Castro]

On 1/23/2024 at 8:55 PM, mont222 said:

At the same time, many other controllers integrated into SCADA via Modbus successfully connect to both servers, only Unitronics v570 connects to the one that polls first.

Don't waste your time asking for a decent Modbus TCP implementation.

Vision series are cheap PLCs with incredible versatility. I already tried every possible workaround regarding Modbus TCP communication. And you are right, other controllers do that kind of stuff better. 

Modbus TCP in the unitronics vision series is Intended to communicate 1 device to 1 PLC at a time per socket.

There are workarounds but you need either use UDP.  Or somehow manage some type of disconnect/reconnect sequence which at the very best will be  finicky.

It  is what it is. On my previous job I inherited abig ammount of systems built on unitronics platform and Invested a lot of time figuring out how to upgrade the systems whitout replacing the PLCs.

 

 

 

 

[Flex727]

2 hours ago, Fernando Castro said:

Or somehow manage some type of disconnect/reconnect sequence which at the very best will be  finicky.

I have a V1210 in the field that connects to 15 different devices using MODBUS TCP with a single socket with this technique. It has been working flawlessly for 10 years without a hiccup. It takes a little over a minute to work its way to all 15, but it's functional.