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Offline Arthur Stunf  
#1 Posted : Monday, November 19, 2018 4:26:36 AM(UTC)
Arthur Stunf

Rank: Newbie

Joined: 11/19/2018(UTC)
Posts: 1

We are using our OPC DA client since many years (about 18). It is a 32 bit windows application and working fine with several OPC servers.
Now we decide to change it to 64 bit and to a service. It is working like the old application but there are some issues.

1. issue

The service is starting automatically with the system. The OPC server is started by COM and works. But sometimes it stoppes after an amount of time.
Theres seems to be no prolem with the server, it's just stopping like having no client.
As the server is not available the client gets an exception on the next interface call...

I can see this problem with different OPC servers.

I have installed the Matrikon Simulation server as well to test it on my system:
- istalling it as a program -> it stops
- installing it as service -> no problem ?!

It seems that the problem does not occure with a service... But I am not able to install all of the used OPC Servers as service.

2. issue

When I start my service using one of the older OPC Servers and try to connect the same one with an other application (e.g. Matrikon Explorer) the OPC Server is starting twice...
The two instances of the OPC Server cause some bigger problems on the system then.
With the Maktrikon Simulation Server I do not have this problem, it starts only one instance.

I assume some kind of registry problem? dcomcnfg looks identically for the servers.

Offline Roger Fortune  
#2 Posted : Thursday, May 30, 2019 7:18:46 PM(UTC)
Roger Fortune

Rank: Advanced Member

Joined: 10/21/2014(UTC)
Posts: 105

Was thanked: 35 time(s) in 32 post(s)
Hi Arthur,
It is standard behaviour for our OPC Servers to stop after a while if no OPC Clients are connected. When an OPC Client connects to the OPC Server, if it is not running it will start, provided the user that the OPC Client is presenting as has launch and activation permissions in the DCOM for the OPC Server. If you take a look at the Simulation Server user manual, there is a registry modification you can do to prevent it shutting down with no clients connected.

As a side note, please be aware that not all 64 bit / 32 bit combinations are compatible. If an OPC Server is an in-process (inproc) type, which means it is a DLL that is loaded into the OPC Client's memory space, this will be a problem if the client and server are not the same "bitness".

Issue two is most likely a DCOM identity issue. Please check DCOM for the OPC Server that is launching twice and choose the identity tab. Change the setting from "Launching User" as this will be causing the issue of duplicate instances.
thanks 1 user thanked Roger Fortune for this useful post.
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