We are currently using a free trail version of KEP Server for our OPC to communicate with our PLC. We were wondering if anyone knows of any good open source OPC software.
Some vendors offer OPC servers for free with their PLCs, but I haven't seen any free OPC servers that supports multiple vendors like KepWare OPC server does. Neither free (unless you count time limited ones), neither open source ones. That saying, the best bet you can get is to get Delphi and make your own OPC servers and clients with free sources found here. I am not aware of free OPC server sources for other languages.