Errors

If you are unable to connect an OPC Client to an OPC Server, chances are the COM and DCOM security settings are not configured correctly on the system(s). All OPC communicates over Microsoft ActiveX COM and DCOM, and you must open your securities to allow data flow. We would recommend checking your default DCOM settings, OPC Client DCOM settings (if available), and OPC Server DCOM settings in this case. To change these, you will have to access the DCOMCNFG tool and allow this communication. This holds true for both a user account, and the system account.  You can configure your COM and DCOM through use of the following documents (in pdf format):

DCOM on Windows NT/2000
DCOM on Windows XP/XP SP1/2003
DCOM on Windows XP SP2/2003 SP1

If you are experiencing DCOM issues across domains or while using workgroups, we strongly recommend downloading and installing MatrikonOPC Tunneller. MatrikonOPC Tunneller eliminates DCOM setup headaches and gets data flowing seamlessly between your servers and clients using TCP/IP.  Tunneller can also be used to ensure secure communication across firewalls.