The pull protocol is one half of a pipeline pattern. The other half is the push protocol.
In the pipeline pattern, pushers distribute messages to pullers. Each message sent by a pusher will be sent to one of its peer pullers, chosen in a round-robin fashion from the set of connected peers available for receiving. This property makes this pattern useful in load-balancing scenarios.
The nng_pull0_open() functions create a puller socket.
This socket may be used to receive messages, but is unable to send them.
Attempts to send messages will result in NNG_ENOTSUP.
When receiving messages, the pull protocol accepts messages as they arrive from peers. If two peers both have a message ready, the order in which messages are handled is undefined.
Only version 0 of this protocol is supported. (At the time of writing, no other versions of this protocol have been defined.)