RELAY

Real-time Embedded Link Abstraction Yoke

RELAY is the shared specification and library for the SoundMatt embedded network protocol ecosystem. CAN, DDS, LIN, MQTT, RCP, and SOME/IP implementations in Go, C, C++, and Rust build against RELAY to share canonical types, interface contracts, error semantics, and a common application API.

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Protocol coverage

Protocol	Go	C	C++	Rust
CAN	go-CAN	—	cpp-CAN	rust-CAN
DDS	go-DDS	—	cpp-DDS	rust-DDS
LIN	go-LIN	—	cpp-LIN	rust-LIN
MQTT	go-MQTT	—	cpp-MQTT	rust-MQTT
RCP	go-RCP	c-RCP	cpp-RCP	rust-RCP
SOME/IP	go-SOMEIP	—	—	—

Specification

Full specification: spec/relay-spec.md
Machine-readable version: spec/version.json
Change history: spec/CHANGELOG.md

Current: v2.9 (stable)

Install

go get github.com/SoundMatt/RELAY/v2@latest

Install the CLI:

go install github.com/SoundMatt/RELAY/v2/cmd/relay@latest

Usage

import relay "github.com/SoundMatt/RELAY/v2"

// All protocol adapters satisfy relay.Node
var node relay.Node = can.Adapt(bus)

// Send — identical regardless of underlying protocol
err := node.Send(ctx, relay.Message{
    Protocol: relay.CAN,
    ID:       "256",      // CAN frame 0x100; DDS topic; MQTT topic; RCP ByteBusID…
    Payload:  data,
})

// Subscribe
ch, err := node.Subscribe(
    relay.WithChannelDepth(128),
    relay.WithBackPressure(relay.DropOldest),
)
for msg := range ch {
    fmt.Printf("%s %s %x\n", msg.Protocol, msg.ID, msg.Payload)
}

// Request/response (RCP, SOME/IP)
if caller, ok := node.(relay.Caller); ok {
    resp, err := caller.Call(ctx, relay.Message{
        Protocol: relay.RCP,
        ID:       "9", // decimal ByteBusID
        Payload:  data,
    })
}

CLI

Usage: relay <command> [flags]

Command	Description
version [--format text|json]	Print tool and spec version
capabilities	Print RELAY tooling capabilities document
status	Print RELAY tooling status document
conform <bin>	Verify that <bin> conforms to the RELAY spec
convert	Reference canonical-value → relay.Message conversion (stdin→stdout)
interop <bin>...	Check implementations are behaviourally interchangeable
crossbar	Route relay.Messages between protocol spokes (--config)
probe	Discover RELAY-conformant binaries
trace	Capture or replay a relay.Message stream
report	Cross-implementation conformance report
sbom	Print the software bill of materials
safety-case	Summarise the safety evidence set
audit-pack	Bundle all safety evidence into a zip
compare	Compare two implementations for interchangeability
versions	List implementations and their spec alignment
serve	Serve a web dashboard, JSON API, and status badge

Conformance

relay conform <binary>

Roadmap

See ROADMAP.md.

Contributing

Sign-off required on every commit (DCO):

git commit -s -m "feat: description"

License

Mozilla Public License 2.0 — see LICENSE.