Errors

If your OPC Client is not able to browse for OPC Servers, it is likely due to the COM/DCOM permissions of your OPCEnum utility. OPCEnum is a tool distributed by the OPC Foundation which browses the registry and returns a list of OPC Servers installed on the machine. If the OPC Client does not have adequate permissions to use the utility, it may not provide you with a list of OPC Servers. To change these permissions, you will have to access the DCOMCNFG tool and allow this communication. You can configure your COM and DCOM through use of the following documents (in pdf format). Configure your system defaults, OPCEnum, and your OPC Client configuration (if applicable).

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 will behave as an OPC Client on the local OPC Server machine and will be better able to access OPCEnum. It also eliminates DCOM setup headaches and gets data flowing seamlessly between your servers and clients using TCP/IP.  Tunneller can be used to ensure secure communication across firewalls.