Each JSON NetworkMessage can contain one or more JSON DataSetMessages. The JSON NetworkMessage is a JSON object with the fields defined in Table 163.
Table 163 – JSON NetworkMessage definition
|
Name |
Type |
Description |
|
MessageId |
String |
A globally unique identifier for the message. The unique identifier can be created by converting a Guid to a String or through another algorithm that creates a unique string. This value is always present. |
|
MessageType |
String |
This value shall be “ua-data” for NetworkMessages containing DataSetMessages. This value is always present. |
|
PublisherId |
String |
A unique identifier for the Publisher. It identifies the source of the message. The presence of the value depends on the setting in the JsonNetworkMessageContentMask. The source is the PublisherId on a PubSubConnection (see 6.2.7.1). If the PublisherId is a UInteger, the UInteger value is converted to a String without leading zeros. |
|
WriterGroupName |
String |
The name of the WriterGroup which created the NetworkMessage. The presence of the value depends on the setting in the JsonNetworkMessageContentMask. |
|
DataSetClassId |
String |
The DataSetClassId associated with the DataSets in the NetworkMessage. The DataSetClassId is a Guid and shall be converted to a String. The presence of the value depends on the setting in the JsonNetworkMessageContentMask. If specified, all DataSetMessages in the NetworkMessage shall have the same DataSetClassId. The source is the DataSetClassId on the PublishedDataSet (see 6.2.3.3) associated with the DataSetWriters that produced the DataSetMessages. |
|
Messages |
* |
A JSON array of JSON DataSetMessages (see 7.2.5.4). This value is always present. |
All fields with a concrete DataType defined are encoded using reversible OPC UA JSON Data Encoding defined in OPC 10000-6.
The fields in the JSON NetworkMessage are controlled by the NetworkMessageContentMask of the JSON NetworkMessage mapping(see 6.3.2.1.1).
If the NetworkMessageHeader bit of the NetworkMessageContentMask is not set, the NetworkMessage is the contents of the Messages field (e.g. a JSON array of DataSetMessages).
If the DataSetMessageHeader bit of the NetworkMessageContentMask is not set, the content of the Messages field is an array of content from the Payload field for each DataSetMessage (see 7.2.5.4).
If the SingleDataSetMessage bit of the NetworkMessageContentMask is set, the content of the Messages field is a JSON object containing a single DataSetMessage.
If the NetworkMessageHeader and the DataSetMessageHeader bits are not set and SingleDataSetMessage bit is set, the NetworkMessage is a JSON object containing the set of name/value pairs defined for a single DataSet.
If the JSON encoded NetworkMessage size exceeds the Broker limits the message is dropped and a PubSubTransportLimitsExceeded Event is reported.