The NetworkMessage flags used with the discovery announcement messages shall use the following bit values.
- UADPFlags bits 5 and 6 shall be false, bits 4 and 7 shall be true
- ExtendedFlags1 bits 3, 5 and 6 shall be false, bit 4 and 7 shall be true
- ExtendedFlags2 bit 1 shall be false and the NetworkMessage type shall be discovery announcement
The setting of the flags ensures a known value for the first three bytes plus the PublisherId in the NetworkMessage, except for the Chunk bit 0 in ExtendedFlags2. The actual security settings for the NetworkMessage are indicated by the SecurityHeader.
The encoding of the discovery announcement header structure is specified in Table 149.
Table 149 – Discovery announcement header structure
|
Name |
Type |
Description |
|
AnnouncementType |
Byte |
The following types of discovery announcement messages are defined. 0Reserved 1Publisher Endpoints message (see 7.2.4.6.6) 2DataSetMetaData message (see 7.2.4.6.4) 3DataSetWriter configuration message (see 7.2.4.6.9) 4PubSubConnection configuration message (see 7.2.4.6.8) 5 OPC UA Application information message (see Table 150) |
|
SequenceNumber |
UInt16 |
Sequence number, incremented by exactly one, for each discovery announcement sent in the scope of a PublisherId. |
The encoding of the OPC UA Application information announcement message structure is specified in Table 150.
Table 150 – OPC UA Application information announcement message structure
|
Name |
Type |
Description |
|
ApplicationInformationType |
UInt16 |
The following types of application information are defined. 0Reserved 1Application description (see 7.2.4.6.5) 2Status (see 7.2.4.6.7) |