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Peer Descriptor Format

A peer descriptor string specifies a range of participants at a given locator. Peer descriptor strings are used in the DISCOVERY QosPolicy (DDS Extension) initial_peers field (see Setting the ‘Initial Peers’ List) and the DomainParticipant’s add_peer() and remove_peer() operations (see Adding and Removing Peers List Entries).

The anatomy of a peer descriptor is illustrated in Example Peer Descriptor Address Strings using a special "StarFabric" transport example.

Figure 1 Example Peer Descriptor Address Strings

A peer descriptor consists of:

These are separated by the '@' character. The separator may be omitted if a participant ID limit is not explicitly specified.

The "participant ID limit" only applies to unicast locators; it is ignored for multicast locators (and therefore should be omitted for multicast peer descriptors).

Locator Format

A locator string specifies a transport and an address in string format. Locators are used to form peer descriptors. A locator is equivalent to a peer descriptor with the default participant ID limit (4).

A locator consists of:

These are separated by the "://" string. The separator is specified if and only if a transport name is specified.

If a transport name is specified, the address may be omitted; in that case all the unicast addresses (across all transport plug-in instances) associated with the transport class are implied. Thus, a locator string may specify several addresses.

If an address is specified, the transport name and the separator string may be omitted; in that case all the available transport plug-ins for the Entity may be used to parse the address string.

The transport names for the built-in transport plug-ins are:

Address Format

An address string specifies a transport-independent network address that qualifies a transport-dependent address string. Addresses are used to form locators. Addresses are also used in the DISCOVERY QosPolicy (DDS Extension) multicast_receive_addresses and the DDS_TransportMulticastSettings_t::receive_address fields. An address is equivalent to a locator in which the transport name and separator are omitted.

An address consists of:

The network and transport addressed are separated by the '#' character. If a separator is specified, it must be followed by a non-empty string that is passed to the transport plug-in. If the separator is omitted, it is treated as a transport address with an implicit network address (of the transport plugin). The implicit network address is the address used when registering the transport: e.g., the UDPv4 implicit network address is

The bits resulting from the transport address string are prepended with the network address. The least significant NDDS_Transport_Property_t::address_bit_count bits of the network address are ignored.

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