I have installed v1.14.0 and, unfortunately, I am still getting the message ‘Modbus Error FC 0x3 timeout’.
In addition, I carried out the following actions and tried again:
It’s still not working.
I have implemented a new setting to allow you to configure the Modbus Unit ID (Slave ID) for the inverter.
By default, GoodWe inverters use ID 247 (0xF7), but some configurations (especially those using a LAN module instead of Wi-Fi) use ID 1.
How to fix it:
That’s great. However, nothing can be done based on such information.
I am sorry if you provide it already, but what is your device, what driver you are using and what exactly did you do to test if it is working (like modbus test, etc.)?
No problem Michal,
I have a gw10K-et-20 with a Wi-Fi / LAN 2.0 dongle and three battery racks, all running the latest firmware. The dongle is connected via the LAN port. The cloud connection works perfectly.
I have enabled Modbus TCP in the Solar-Go app, but I cannot configure any further settings there;
I have checked via the terminal whether port 502 is open
I hope you can help me; if you need any further information, please let me know
Thank you for the very detailed information and the connection test. It helps to identify the issue.
The problem is a protocol mismatch:
• The Inverter: Your Test-NetConnection confirms that port 502 is open and listening for TCP connections.
• The Homey App: This app currently uses UDP (specifically designed for the default GoodWe port 8899).
Even if the IP and port are correct in the settings, a UDP request sent to a TCP port will always result in a Timeout because the inverter is “listening” for a different type of handshake. This is why it works for others; most Wi-Fi dongles use port 8899 which operates over UDP.
What you can try now:
Check Port 8899: In your Homey device settings, change the port from 502 to 8899.
◦ Many GoodWe dongles support both protocols simultaneously. If your dongle still has the UDP service active, it should start working immediately.
Verify Unit ID: If you use port 8899, keep the Modbus Unit ID at 247 (or 1 if that fails).
Please let me know if switching to port 8899 in the Homey settings solves it for you!
Hi Michal,
Unfortunately, it still isn’t working, and I get the same timeout message on port 1 and port 247
I’ve also checked whether port 8899 is open and I get the following message:
Is there anywhere I can check whether the UDP service on my dongle is still active? To be sure, I disconnected the WiFi/Lan 2.0 dongle from the power supply for 10 seconds.
Just to be clear, I’m using the Modbus ET, not the EX-30 version in your app.
Do you have any other suggestions?
Hi, I think I may have found the reason why your solution doesn’t work with my setup.
My WiFi/LAN Kit 2.0 is communicating via Modbus TCP on port 502, while your app uses the UDP protocol on port 8899. I tested a GoodWe UDP/8899 request directly against my inverter, but got no response, while Modbus TCP on port 502 works perfectly.
So I suspect the difference is simply the communication protocol supported by my particular WiFi/LAN Kit. Your approach may work perfectly with other GoodWe dongles, but apparently not with mine.
At least now I think we understand why I could never get your app to connect. 
Hi @Michal_Stranik do you have any other suggestions or solutions? Unfortunately, I can’t get it to work, and I’m out of options.
