Professional OPC
Development Tools

logos

Online Forums

Technical support is provided through Support Forums below. Anybody can view them; you need to Register/Login to our site (see links in upper right corner) in order to Post questions. You do not have to be a licensed user of our product.

Please read Rules for forum posts before reporting your issue or asking a question. OPC Labs team is actively monitoring the forums, and replies as soon as possible. Various technical information can also be found in our Knowledge Base. For your convenience, we have also assembled a Frequently Asked Questions page.

Do not use the Contact page for technical issues.

Wait between connection and actual subscription

More
22 Apr 2016 07:27 #4010 by support
Dear Sir,
unfortunately there is no such feature built into the product; but there are workarounds.

(BTW, I am sure you realize that if the OPC server indeed behaves as described, it is a bug in the server that should be primarily handled in there).

You can try to subscribe first with just one item, wait for some time, and then proceed with your other (many( subscriptions. The first item does not even have to be a valid one; in fact, choosing an invalid one (e.g. unknown Item ID) would probably be better, because it should be rejected right away and won't consume anything on the server side later.

It is also possible to achieve a similar effect by a dummy one-time operation, such as Read or Browse. In this case, however, care should be taken so that the wait delay is shorter than the (configurable) Hold period of the client, otherwise the connection might be closed before the "real" subscription occurs (which would then cause a re-connection, defeating the purpose).

Best regards

Please Log in or Create an account to join the conversation.

More
21 Apr 2016 09:09 #4006 by filip.slachmuylders@pa-ats.com
Dear support

Is there a way to have a delay between the connection to the OPC server and the actual start of subscribing values for reading?

Dim WithEvents oEasyDAclient As New OpcLabs.EasyOpc.DataAccess.EasyDAClient
Dim aoReadarray() As OpcLabs.EasyOpc.DataAccess.OperationModel.EasyDAItemSubscriptionArguments
..
oEasyDAclient.SubscribeMultipleItems(aoReadarray)

The reason is that the OPC server seems to hang, when requesting many values, this migh be cause by the fact that the OPC server does not have time to keep up and gets confused resulting in a hanged state

Thanks in advance

Filip

Please Log in or Create an account to join the conversation.

Moderators: support
Time to create page: 0.051 seconds