You have several options.
1.Network variables here is an example Project for this: http://store.codesys.com/mixedsearch/mi ... duct_area=
2. Modbus example will follow
3 Ethernet IP Scanner the other is Ethernet IP Adapter here is an example Project for this
http://forum.codesys.com/viewtopic.php? ... 503#p14144
beside the Elsner Wetterstation there is a communication between Raspberry PI and another CODESYS plc in this application