Functions are relative to the device context.
All calls that are accessing resources is relative to the parent device. For example, if the scripts opens a file the path supplied to the open function must be relative to the device.
Example
Set the host to be the address of the windows computer "domainserver".
TLuaFile:Open("C:\\test.txt");
Calling the function would make the script open the file test.txt located on the C: harddisk of the computer "domainserver".
This is also why all communication related classes such as TLuaFTPClient, TLuaHTTPClient and TLUASocket only takes an port number argument, the IP address is hard coded to the current device by the framework.