Is it possible to poll a Flexy gateway via Modbus if it's already sending data to the DataMailbox?

If a Flexy gateway is set up to record Modbus data and send it into the DataMailbox, is it possible for us to still poll the Flexy gateway using Modbus protocol manually?


It is possible for the Flexy to monitor Modbus tags and poll modbus while sending data to the Mailbox.

Are you experiencing issues?

The Flexy gateway we set up is polling data through modbus and sending that data to the mailbox properly, i.e. it’s recording values within the expected range. The difficulty we’re experiencing at the moment is that we’re having trouble retrieving values from the Flexy gateway through our own modbus poll requests to that same gateway - the requests return without any error code, but all the coils and registers that we poll for are returned as 0, despite the gateway recording non-zero values for those same coils and registers to the mailbox at the exact same time.

I just wanted to make sure that Flexy gateways don’t block external modbus requests since we’re new to Flexy/Ewon products, and were unsure whether this odd condition we’re running into was due to errors in our modbus requests, or some configuration in the Flexy gateway.


Are you publishing your tags correctly with the Flexy?

I would go through the following document to double check the configuration.

Publish tag in Modbus TCP.docx (108.5 KB)

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Thank you! That did the trick, and I can poll the gateway directly now, as long as I’ve set up a connection to the gateway in eCatcher. I have a follow-up question, though, and forgive me if this is a basic one, but I’m very new to working with VPNs: is there any way to configure a Flexy gateway so that I can send Modbus requests to it without needing to establish a VPN connection to it first?


If you are sending Modbus commands externally from the LAN side, you will need to have the VPN established for the connection.

If the commands are coming from within the LAN connection, you do not need the VPN established.

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Forgive me if this is a basic question, but I haven’t worked with VPNs before, and I’m still trying to get the basics down: whether we’re sending Modbus commands from the LAN side depends on the IP address we’ve assigned the gateway in eBuddy, right? Or in other words, if we have a gateway set up that we can currently only send Modbus requests to after establishing a VPN connection to it in eCatcher, we can eliminate the need to establish an eCatcher connection first by changing the IP address and changing nothing else? Or would some additional steps besides just changing the IP address be required? Thanks in any case for your ongoing help.


IF you are strictly sending commands on the LAN side. You will only need to configure the LAN IP address to be in the same range.

With eCatcher, it is a little bit different. While you will be connecting to the LAN IP remotely, you will need to verify that you are able to ping the LAN IP. You can also use the VPN IP when connecting remotely.

I just want to make sure I understand, then: we can’t include a physically-remote Flexy gateway into our office LAN by just changing the IP address using eBuddy, and therefore the only way to send a Modbus command to a physically-remote Flexy gateway is to first establish a VPN connection to it through eCatcher. Right?


If you a physically connected to the Ewon unit on the LAN, you can send commands through LAN network.

If you are outside of the LAN, you will need to use eCatcher.

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