@Nagarjuna-Reddy So this indicates the issue is on the Server side. It is possible that your client is causing the Server side to fail, but it is the Server side code that needs to recover the port state. Do you have any control over the Server? What type of app is it running?

@Nagarjuna-Reddy So it seems the underlying issue is that your DHCP server is either not accessible or is not providing dhcp service correctly. Using static IP is a fix but your IP, routing and DNS should be provided by your DHCP server on your network.

@Ghofran-Daoues this is not really a question for this forum, it's really for a libmodbus forum. However, your error indicates it cannot connect to port 502 of the device. There can be a few reasons for this, the first things I would look at are 1) perhaps the device is not accessible on your network; 2) the device is not listening on port 502. To check 1, see if you can ping the device (ping <ip address>) To check 2, (assuming check 1 passes) check your modbus device is listening on port 502 using nmap (nmap -p 502 <ip address>) nmap should report the port is "open" but if it shows as closed, there's your problem, if it reports as "filtered" there is probably a firewall blocking you.

@Vyacheslav-Bachynskyi We made some upgrades to the firmware server so there was some downtime last week. Should be running smoothly now. Let me know if it isn't! @Thorsten-Ludewig The Omega is most likely having issues connecting to your WiFi network. Can you please make an issue at https://github.com/OnionIoT/wdb40/issues and I'll provide support.