Once a peer is located, its capabilities and status may be queried. The PIP provides a generic framework for obtaining peer status and monitoring information. Peers are not required to respond to PIP requests. A reliable transport is optional.
peer information messages may be
sent. Zero, one, or multiple responses may
be received in response to a peer information query. The
PIP is layered on the PRP. A
QueryID field is used
for matching PIP queries to the PIP responses.
The PIP query message provides a request field that may be used to encode a specific request. The PIP does not dictate the format of the request field. Higher-level services could utilize the request field for adding expanded capabilities.
The PIP is composed of a query message, which is sent to query a peer for its current state and other relevant information (see Example 17-6). A query without a defined request field returns a default set of information about a peer (i.e., uptime, message count, etc.).
Example 17-6. Query message schema
<xs:element name="PeerInfoQueryMessage" type="jxta:PeerInfoQueryMessage"/> <xs:complexType name="PeerInfoQueryMessage"> <xs:element name="sourcePid" type="xs:anyURI"/> <xs:element name="targetPid" type="xs:anyURI"/> <xs:element name="request" type="xs:anyType" minOccurs="0"/> </xs:complexType>
The elements in Example 17-6 are:
The source peer ID of the requesting peer
The destination peer ID ...