Protocols implemented by nanonext.
For an authoritative guide please refer to the online documentation for the NNG library at https://nng.nanomsg.org/man/.
Bus (mesh networks)
[protocol, bus] The bus protocol is useful for routing applications or for building mesh networks where every peer is connected to every other peer.
In this protocol, each message sent by a node is sent to every one of its directly-connected peers. This protocol may be used to send and receive messages. Sending messages will attempt to deliver to each directly connected peer. Indirectly-connected peers will not receive messages. When using this protocol to build mesh networks, it is therefore important that a fully-connected mesh network be constructed.
All message delivery in this pattern is best-effort, which means that peers may not receive messages. Furthermore, delivery may occur to some, all, or none of the directly connected peers (messages are not delivered when peer nodes are unable to receive). Hence, send operations will never block; instead if the message cannot be delivered for any reason it is discarded.
Pair (two-way radio)
[protocol, pair] This is NNG's pair v0. The pair protocol implements a peer-to-peer pattern, where relationships between peers are one-to-one. Only one peer may be connected to another peer at a time, but both may send and receive messages freely.
Normally, this pattern will block when attempting to send a message if no peer is able to receive the message.
Poly (one-to-one of many)
[protocol, poly] This is NNG's pair v1 polyamorous mode. It allows a socket to communicate with multiple directly-connected peers.
If no remote peer is specified by the sender, then the protocol will select any available connected peer.
If the peer on the given pipe is not able to receive (or the pipe is no longer available, such as if the peer has disconnected), then the message will be discarded with no notification to the sender.
Push/Pull (one-way pipeline)
In the pipeline pattern, pushers distribute messages to pullers, hence useful for solving producer/consumer problems.
If multiple peers are connected, the pattern attempts to distribute fairly. Each message sent by a pusher will be sent to one of its peer pullers, chosen in a round-robin fashion. This property makes this pattern useful in load-balancing scenarios.
[protocol, push] The push protocol is one half of a pipeline pattern. The other side is the pull protocol.
[protocol, pull] The pull protocol is one half of a pipeline pattern. The other half is the push protocol.
Publisher/Subscriber (topics & broadcast)
In a publisher/subscriber pattern, a publisher sends data, which is broadcast to all subscribers. The subscriber only see the data to which they have subscribed.
[protocol, pub] The pub protocol is one half of a publisher/subscriber pattern. This protocol may be used to send messages, but is unable to receive them.
[protocol, sub] The sub protocol is one half of a publisher/subscriber pattern. This protocol may be used to receive messages, but is unable to send them.
Request/Reply (RPC)
In a request/reply pattern, a requester sends a message to one replier, who is expected to reply with a single answer. This is used for synchronous communications, for example remote procedure calls (RPCs).
The request is resent automatically if no reply arrives, until a reply is received or the request times out.
[protocol, req] The req protocol is one half of a request/reply pattern. This socket may be used to send messages (requests), and then to receive replies. Generally a reply can only be received after sending a request.
[protocol, rep] The rep protocol is one half of a request/reply pattern. This socket may be used to receive messages (requests), and then to send replies. Generally a reply can only be sent after receiving a request.
Surveyor/Respondent (voting & service discovery)
In a survey pattern, a surveyor sends a survey, which is broadcast to all peer respondents. The respondents then have a chance to reply (but are not obliged). The survey itself is a timed event, so that responses received after the survey has finished are discarded.
[protocol, surveyor] The surveyor protocol is one half of a survey pattern. This protocol may be used to send messages (surveys), and then to receive replies. A reply can only be received after sending a survey. A surveyor can normally expect to receive at most one reply from each responder (messages may be duplicated in some topologies, so there is no guarantee of this).
[protocol, respondent] The respondent protocol is one half of a survey pattern. This protocol may be used to receive messages, and then to send replies. A reply can only be sent after receiving a survey, and generally the reply will be sent to the surveyor from which the last survey was received.