I think the answer is Yes, and No…
Thank you for the link - I had not seen that one, and it is very informative. Another way of getting data by proxy between the logger and the cloud. Good solution (keep both, no extra hardware) if you can get it to work.
My direct experience is with an old (probably V2) LAN connection data logger. This has an older interface with connectable server ‘B’, as well as an internal (and settable) Modbus port. Both of which I have been able to use (push out data, connect Modbus over TCP). Incidentally, my stick pushes out a data block of 250 bytes, which does not compare with any of the more recent data block lengths at all. Since Solarman (Solis) updated their cloud offering a few months ago, my stick has connection issues and locks up after a few minutes, only coming back around every three hours. Clearly an issue with it not managing the (V5) heartbeat and keep alive messages.
I also have a newer version (V4?) stick which does not want to connect to the inverter, but has the later web pages, where the server ‘B’ does not work and neither does the config_hide stuff. As it won’t connect to the inverter I cannot use it let alone effectively test the settings. I also only have LAN sticks, which are quite different to the WiFi ones, although the later LAN stick assumes it is a WiFi model and wants SSIDs, even though it is a LAN stick and has no physical WiFi.
The latest protocol, V5, is becoming better documented. I also found this
https://pysolarmanv5.readthedocs.io/en/latest/index.html
As far as I can tell, Solarman have always used ‘Modbus over TCP’ in one form or another to connect to the cloud. Now (V5) use Modbus (over TCP) data packets, which are encapsulated into a proprietary message set (both message package and message sequences). The WiFi modules use chipsets that work to port 8899 by default, and older ‘open’ ports have been removed from the firmware settings.
I think the short answer is, yes you can get to the data via TCP connection, on port 8899. The IP address is a local (private) one, so probably should reflect the IP address of your stick. However, I suspect that a) this is encapsulated in the V5 protocol, and b) it appears it does not work with Solis S3-WIFI-ST. A guess is that some brandings (eg Solis) have complicated the setup even further!
All somewhat confusing, difficult to work out what is going on, what any particular stick actually is/does, and challenging to connect to. After months of working on this I have now given up on all my sticks, turned it off, and gone down a direct physical connection to the inverter RS485 port to connect directly with Modbus (over TCP via a serial-ethernet adaptor).
I wish you every success in your endeavours!