7.2.4.6.3 Discovery announcement header
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 168.
| Name | Type | Description |
| AnnouncementType | Byte | The following types of discovery announcement messages are defined. 0 Reserved 1 Publisher Endpoints message (see 7.2.4.6.6) 2 DataSetMetaData message (see 7.2.4.6.4) 3 DataSetWriter configuration message (see 7.2.4.6.9) 4 PubSubConnection configuration message (see 7.2.4.6.8) 5 OPC UA Application information message (see Table 169) 6 ActionResponder configuration message (see 7.2.4.6.10) 7 ActionMetaData announce message (see 7.2.4.6.11) |
| 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 169.