I need to realize OPC server, on Windows XP. I download OPC library, and OPC client (application not library). I realize my OPC server, when i use client on my machine all runs normally. But when i connect from remote computer i do not see my server. I understand that the technology dkom potentially dangerous. I get this manual, and did everything on it, but nothing changed. I disable my windows firewall, add 135 port in windowds firewall exception. In dcomcnfg grants local and remote access to "anonymous" and "all" groups, grants local and remote launch & activation to "administrators" and "all" groups. And nothing changed, i did not give the right of my DCOM component because i thought the following: i get list of servers not work with them. In my microsoft network no domain and active directory, can i achieve the desired result in this case?
2 Answers
There's a number of things which can go wrong with OPC DA over DCOM. From the top of my head, you could try the following:
- Check if OPCEnum service is running on the server computer. This service provides the list of OPC servers on to the potential clients. It's part of the OPC foundation redistributable.
- Make sure that whatever dcomcnfg changes you applied, they are done both on the server and client computer.
- If you're using only local users, try creating a dedicated user for OPC access on both server and client computer, e.g. call him "opc". Then grant all the rights to this user in "COM security" section of dcomcnfg. Run both the server and client as "opc". Make sure the local users authenticate as themselves (see "Security options" in local policies).
- If all else fails, a workaround can be to deploy the server on the client computer, register it, then remove it. Worked for me once.
The most common error is DCOMs have not been configured properly. I find this guide very useful:
Also this other guide gives you a big understanding of a Remote OPC DA:
I had a similar problem when I tried to communicate with a remote OPC server in a different PC. Please pay attention to the point number 2 of the second guide (2.Users and Groups), make sure both PCs are logging in under the same user account with the same password.
2.1 Domains and Workgroups When working within a workgroup, each user will need to be created locally on each computer involved in the connection. Furthermore, each user account must have the same password in order for authentication to occur. A blank password is not valid in most cases. Because changes may need to be made to the local security policy on each computer, remote connectivity within a workgroup has the potential to be the least secure connection. For more information, refer to Local Security Policies. When working within a domain, local users and groups are not required to be added to each computer. A domain uses a central database that contains the user accounts and security information. If working within a domain is preferred, a network administrator may have to implement the changes. Mixing domains and workgroups will require both computers to authenticate with the lesser of the two options. This means that the domain computer will require the same configuration as it would if it were on a workgroup. Local user accounts must be added to the domain computer.
