Looking to send/recieve real time data between PC - PLC

Hi, I'm pretty new to plc programming. My current project at work is to design a c++ program that will be able to communicate to an allen bradley SLC 505 plc via ethernet. ultimatly, i'm looking for the pc to recieve data from the plc, use that data to search an sql database, and then return a value from the database back to the plc. Is there any source code or drivers to do the communications? i would prefer freeware, just to see if I would be able to do it. Then I could spend money on a more expensive package if i need to.

Thanks a lot for all your help.

ABEL

Search for Ron Gage's ABEL - Allen Bradley Ethernet Library. It's a Linux-based set of programs for talking AB-ethernet. I have no clue as to how hard it would be to translate that to a Windows C++ platform.

But I'm not aware of any freeware communications drivers, but several companies sell communication drivers, some with downloadable demo versions which will work for a period of time or with limited functionality.

RSLinx OPC-Server/read/write-methods or DDE could be usable with ethernet or everything what RSLinx support.