If you plan on using your Raspberry Pi with the Edge Microserver to connect to a PLC with the Modbus protocol, then you need to follow the instructions here: https://community.thingworx.com/community/developers/blog/2015/12/13/modbus-plc-simulator
But in addition to that also consider that:
1. The modbusExample.lua tries to load file transfer functionality.
2. There is something wrong with the supplied core.so file (maybe it was not compiled for ARM architecture) - you get No such file or directory
[ERROR] when running the luaResource.
To fix the 1st issue is easy... just remove the require "thingworx.shapes.filetransfer" line from modbusExample.lua.
To fix the second issue you need to find a core.so file which is compatible with the ARM Architecture of your Raspberry Pi. In theory, the core.os file supplied as part of the TWEMS MODBUS Package_Linux_ARM.zip file located at microserver/etc/community/clibs/socket/core.so should work, but it does not.
Download the lua-socket resource:
$ sudo apt-get install lua-socket
Copy the new core.so to your microserver installation:
$ cp /usr/lib/arm-linux-gnueabihf/lua/5.1/socket/core.so /home/pi/microserver/etc/community/clibs/socket/
This should yield success.