PPS clients can subscribe to multiple objects, and PPS objects can have multiple subscribers. When a publisher changes an object, all clients subscribed to that object are informed of the change.
To subscribe to an object, a client simply calls open() for the object with O_RDONLY to subscribe only, or O_RDWR to publish and subscribe. The subscriber can then query the object with a read() call.
A read returns the length of the data read, in bytes. If the allocated read buffer is too small for the data being read in, the read fails.