The NetworkMessage flags used with the discovery announcement messages shall use the following bit values.

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)