Implement cpppo.server.enip.historize, an example of customizing
an EtherNet/IP Controller simulator, to integrate the stream
of client PLC I/O requests with your own application.
o Modify cpppo.server.enip.main to accept a device.Attribute
  derived class via the attribute_class keyword argument.  This
  class may be used to intercept all PLC I/O.
o Version 2.7.1