Help about TCP/IP and connect with PLC

Can someone help pls
My friend has a project about Arduino+Ethernet shield modbus TCP/IP(Ethernet shield W5100) and PLC Siemens S7-1200.He wants to connect Arduino with PLC using TCP/IP protocol through Ethernet Shield . So my questions are :

  • How we can do it?
  • If you have any source code which concern about this,will you share it for me please?

Thanks for read this topic