I cannot offer specific help, since I'm not using the same stack as you. But, I do Modbus/TCP quite a lot and can offer this:
We make our money on hardware, so give our software free. One extrememly useful piece is horribly named zapreg32.exe; it's a command-line register viewer which supports many protocols, including Modbus/TCP (and several serial protocols).
We do not have it as a standalone download, but it is in this archive:
which you could install, or use an archiving tool to extract only zapreg32.exe into a directory in your PATH.
Then you would:
zapreg32 10.10.10.100 255 -s
where 10.10.10.100 is your server (duh) and 255 is the Destination Index to put in the messages. This will read 4x (%MW) registers by default, switch -3 reads 3x, -1 and -0 (I believe) display 1x and 0x register spaces. The -s switch turns off polling for identity strings supported by only our products.
It was written as a tool for internal use, but is extremely useful in troubleshooting too--lets us eliminate our bridge as a problem and say something to the effect of "Now you need to check the configuration on your SCADA"...
Good luck,