Annex C (normative) OPC UA Mapping to mDNS ToC Previous Next

C.2 DNS Text (TXT) Record Syntax ToC Previous Next

The SRV record has a TXT record associated with it that provides additional information about the DiscoveryUrl. The format of this record is a sequence of strings prefixed by a length. This specifications adopts the key-value syntax for TXT records described in DNS-SD.

Table 69 defines the syntax for strings that may in the TXT record.

Table 69 – DNS TXT Record String Format

Key-Value Format Description
path=/<path> Specifies the text that appears after the port number when constructing a URL. This text always starts with a forward slash (/).
caps=<capability1>,<capability2> Specifies the capabilities supported by the Server.
These are short (<=8 character) strings which are published by the OPC Foundation (see Annex D). The number of capabilities supported by a Server should be less than 10.

The MulticastExtension shall convert DiscoveryUrls to and from these SRV records.

Previous Next