MODBUS

[JingleBells]

Hi, I configured a Smart-UPS SMT1500C in a lab and had it on the network ok. Packed it up and sent it out to a remote site and suddenly the device refuses all connections. I ran a portscan and the only open port is TCP/502 for MODBUS. I have no idea how that happened. I was looking at documentation about APC MODBUS and found that it might be possible to reset the UPS using a MODBUS tool that can write to a register. I have tried a tool that can read register 41357 the UPScommand_BF register and get a value of 16640 dec or 0x4100 hex back. So, I thought I could try and write a value to the register that would have bit 3 set to 1. However, when I do the write nothing happens. Wireshark shows the UPS respond to the write with the value to be written but the next read shows 16640 again. I was wondering if there is anyone that tell me the actual value to write to register 41357 to have the UPS reset? And does that reset the network card so that other ports such as https or ssh are open?