I'm running a Modbus TCP server within node-red. I had a bit of an adventure forwarding the right ports from Docker , and now its signal is reachable from clients (sorry, I know it's master/slave config, but I'm more familiar with server/client analogies). The server log outputs the following: {"ty…

Solution: Turns out there was an error on my colleague's side, where his software was reading from addresses 4001, where it should have been reading from address 1 as they were already denoted as holding registers to begin with and didn't need the 400 preamble.

Is there any visible difference, e.g. is there some sort of bitwise operation that I don't know about that happens with Modbus signals?

I don't understand what you mean by your friends numbers and your numbers. Are you both accessing the same server in the same way?

Same server is being accessed (code above). I am accessing it via node-red installed on my machine (flow above in "Master"); my friend is using some proprietary software, but we're both getting different numbers to what is broadcast.

[image] Darren: Same server is being accessed (code above). Physically the same machine, or the same code on a different machine.

Node-red Modbus Server is running on physical machine A and rebroadcasting signals received from other devices on LAN My node-red Modbus Client is running on a separate physical machine B, connected via VPN to the same LAN as machine A My co-worker's Modbus Client is not node-red and I believe run…

To investigate why the two are different, examine the raw data returned by the modbus requests. That may give a clue as to why they are both wrong.

Isn't raw data what is returned by the modbus read nodes? e.g. Inject --> modbus flex getter --> log. I was under the impression that was it... Or is there a particulare software you could recommend to read the raw data?

[image] Darren: Isn't raw data what is returned by the modbus read nodes? Yes, so you need to compare that with the data your co-worker gets, as he is getting different data. The question is, is it the interpretation of the raw data or the raw data itself that is different.

Weirdest thing is that my raw data read differs from my raw data broadcast. e.g. debug log says I'm broadcasting ABCD, but I receive AXYZ, unless I explicitly force broadcast xOxx or xxOx etc. , then I receive xOxx etc. I'd be more confident in telling him his software is reading wrong if I was sure…

[image] Darren: debug log says I'm broadcasting ABCD, but I receive AXYZ, unless I explicitly force broadcast xOxx or xxOx etc. Sorry, I have no idea what you mean by that.

Modbus TCP previews correct output, but receiving end gets garbage

General

Darren 16 May 2023 16:56 20

Here's another log, straight from the server:

Address	Server output
D401	0x4
D402	0x1e
D403	0x98
D404	0x98

Seems to be in HEX, I wonder if something's getting misinterpreted...

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Modbus TCP previews correct output, but receiving end gets garbage

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