Ethernet Frames Message Queue (EFMQ)

EFMQ provides an MQTT pub/sub style abstraction for Ethernet Frame messaging.

EFMQ is like MQTT for your Local Area Network. Unlike MQTT no remote or local broker is required, message traffic is effectively broadcast peer-to-peer. With EFMQ, messages never leave your network.

Messaging can be two-way. Each node can operate as either a publisher or subscriber, or both.

This package leans heavily on @mdlayher's raw and ethernet packages, which do almost all the heavy lifting.

Usage

Basic publisher and subscriber examples are provided below. Nodes can publish and subscribe to multiple topics.

The API follows a typical MQTT client API loosely.

// Create connection
mq, _ := efmq.NewEFMQ(networkInterface string)

// Publish
mq.Publish(topic string, payload string)

// Subscribe
mq.Subscribe(topic string)

// Unsubscribe
mq.Unsubscribe(topic string)

// List subscriptions
mq.Subscriptions()

// Start listening
mq.Listen()

// Message channel
mq.Message

// Message 
Message struct {
	Topic string
	Payload string
}

Publisher example

The code below will publish data to the fermenter topic every second. en1 is the network interface on Mac (my Mac at least). On a Raspberry Pi it might be wlan0. Use netstat -i to discover.

mq, err := efmq.NewEFMQ("en1") 
if err != nil {
	log.Fatal(err)
}
t := time.NewTicker(1 * time.Second)
for range t.C {
	if err := mq.Publish("fermenter", "20.5"); err != nil {
		log.Fatalln(err)
	}
}

Subscriber example

The code below sets up a subcription to the fermenter topic and then listens for messages. Messages are received on a channel.

mq, err := efmq.NewEFMQ("wlan0")
if err != nil {
	log.Fatal(err)
}
mq.Subscribe("fermenter")
mq.Listen()
for msg := range mq.Message {
	fmt.Println("topic:", msg.Topic)
	fmt.Println("message:", msg.Payload)
}

Todo

• Better test coverage
• Check message does not exceed frame byte data limit (1500 bytes?)