Generic request/response protocols.
General Usage
[RequestResponse] is a NetworkBehaviour that implements a generic
request/response protocol or protocol family, whereby each request is
sent over a new substream on a connection. RequestResponse is generic
over the actual messages being sent, which are defined in terms of a
[RequestResponseCodec]. Creating a request/response protocol thus amounts
to providing an implementation of this trait which can then be
given to [RequestResponse::new]. Further configuration options are
available via the [RequestResponseConfig].
Requests are sent using [RequestResponse::send_request] and the
responses received as [RequestResponseMessage::Response] via
[RequestResponseEvent::Message].
Responses are sent using [RequestResponse::send_response] upon
receiving a [RequestResponseMessage::Request] via
[RequestResponseEvent::Message].
Protocol Families
A single [RequestResponse] instance can be used with an entire
protocol family that share the same request and response types.
For that purpose, [RequestResponseCodec::Protocol] is typically
instantiated with a sum type.
Limited Protocol Support
It is possible to only support inbound or outbound requests for
a particular protocol. This is achieved by instantiating RequestResponse
with protocols using [ProtocolSupport::Inbound] or
[ProtocolSupport::Outbound]. Any subset of protocols of a protocol
family can be configured in this way. Such protocols will not be
advertised during inbound respectively outbound protocol negotiation
on the substreams.