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OPC UA Pub Sub - Understanding Meta Message
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Jothi Sankarraj
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Forum Posts: 29
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04/09/2019
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07/30/2019 - 02:00
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I’m trying to implement a client for reading / decoding / parse “OPC UA Pub Sub” messages that I get from a server. I managed to parse the header section as laid out in Part 14 of the Spec. But I’m kind of stuck after that. 

Here is the parsed message so far!

version [bit 0-3] = 1
publisherIdEnabled [bit 4] = true
groupHeaderEnabled [bit 5] = false
payloadHeaderEnabled [bit 6] = false
extendedFlags1Enabled [bit 7] = true
extendedFlags1 =
publisherIdType [bit 0-2] = String
dataSetClassIDEnabled [bit 3] = false
securityEnabled [bit 4] = false
timeStampEnabled [bit 5] = false
picoSecondsEnabled [bit 6] = false
extendedFlags2Enabled [bit 7] = true

extendedFlags2 =
isChunkMessage [bit 0] = false
promotedFieldsEnabled [bit 1] = false
networkMessageType [bit 2-4] = DiscoveryResponseType

publisherId = Test_Published_Id_81234_DE_1
dataSetClassId = None

So from my understanding, to parse the bytes after the header, I need to check for the NetworkMessageType which in my case is the DiscoveryResponseType. So that would mean that I should assume that the next set of bytes should represent the Discovery Response Header. Is this correct? I should be looking at parsing this information:

7.2.2.4.2.2 Discovery Response Header Table 87 from the Spec?

Is my understanding correct?

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