Modbus master tcp

Hello,

I have an arduino Ethernet.
In my network I have an modbus slave module.
I want to connect to the slave module with my arduino ethernet as an modbus master. (all by tcp)
Has somebody an example sketch for an modbus master over tcp.
I have tried using this one: http://myarduinoprojects.com/modbus.html
But I can’t get it to work.

Thanks
Jan Hein