Modbus TCP multiple registers R/W

I'm looking at: Mudbus.cpp - an Arduino library for a Modbus TCP slave. Copyright (C) 2011 Dee Wykoff

can't get how this library work with MULTIPLES REGISTERS what are the limits, maximum number of word in a message? with Rssim server I can send 125 Word in a message, with a slave server on arduino can't go over 4 word, then errors appears.

Looking at packages with wireshark, there's no response to Query of client, but a TCP segment of a reassembled PDU. Is this supposed to be correct?

Is there anyone who use this library? are there better choice to get a modbus tcp server, up and running?

I use the Mudbus library without any particular problem. It seems strange to me that it does not work with 4 words only. What kind of error did you get?