Snple MQTT

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Note: The API of this library is still unstable and has not been sufficiently tested, please do not use it in production environments.

Features

• MQTT 3.1.1 compatible.
• Full MQTT Feature-set (QoS, Retained, $SYS)
• Trie-based Subscription model.
• Ring Buffer packet codec.
• TCP, Websocket, (including SSL/TLS).
• Interfaces for Client Authentication and Topic access control.
• Bolt-backed persistence and storage interfaces.
• Server Publish (Publish, PublishToClientByID, ...).
• Event hooks (Recv, Send, ...), see hook.go.

Roadmap

• Improve event hooks and server publish interface
• MQTT v5 compatibility

Quick Start

import (
    "github.com/snple/mqtt"
    "log"
)

func main() {
    // Create the new MQTT Server.
    server := mqtt.New()

    // Create a TCP listener on a standard port.
    tcp := listener.NewTCP("t1", ":1883", &mqtt.AuthAllow{})

    // Add the listener to the server.
    err := server.AddListener(tcp)
    if err != nil {
        log.Fatal(err)
    }

    // Start the broker. Serve() is blocking - see examples folder
    // for usage ideas.
    err = server.Serve()
    if err != nil {
        log.Fatal(err)
    }
}

Examples of running the broker with various configurations can be found in the examples folder.

Authentication and ACL

Authentication and ACL may be configured on a per-listener basis by providing an Auth Controller to the listener configuration. Custom Auth Controllers should satisfy the Auth interface found in auth.go. Two default controllers are provided, AuthAllow, which allows all traffic, and AuthDisallow, which denies all traffic.

    tcp := listener.NewTCP("t1", ":1883", &mqtt.AuthAllow{})
    err := server.AddListener(tcp)

If no auth controller is provided in the listener configuration, the server will default to Allowing all traffic.

SSL/TLS

SSL/TLS may be configured on both the TCP and Websocket listeners.

    cert, err := tls.X509KeyPair(publicCertificate, privateKey)
    if err != nil {
        log.Fatal(err)
    }
    cfg := &tls.Config{Certificates: []tls.Certificate{cert}}

    tcp := listener.NewTCPWithTLS("t1", ":1883", &mqtt.AuthAllow{}, cfg)
    err := server.AddListener(tcp)

Note the mandatory inclusion of the Auth Controller!

Data Persistence

Snple MQTT provides a persistence.Store interface for developing and attaching persistent stores to the broker. The default persistence mechanism packaged with the broker is backed by Bolt and can be enabled by assigning a *bolt.Store to the server.

    // import "github.com/snple/mqtt/persistence/bolt"
    err = server.AddStore(bolt.New("mqtt.db", nil))
    if err != nil {
        log.Fatal(err)
    }

Persistence is on-demand (not flushed) and will potentially reduce throughput when compared to the standard in-memory store. Only use it if you need to maintain state through restarts.

Server publish

Snple MQTT provides interfaces such as Publish, PublishToClientByID etc. for publish messages directly from the server.

    server.Publish(
        "time", // topic
        []byte(fmt.Sprintf(`{"time": "%s"}`, time.Now().Format(time.RFC3339))), // payload
        1,     // qos
        false, // retain
    )

    server.PublishToClientByID(
        "mqtt_123456", // client id
        "time",        // topic
        []byte(fmt.Sprintf(`{"time": "%s"}`, time.Now().Format(time.RFC3339))), // payload
        1,     // qos
        false, // retain
    )

With PublishToClientByID, you can publish messages to specified client, even if the client is not subscribed. (It depends on whether your client will handle unsubscribed messages.)

Server Hook interface

Snple MQTT provides a Hook interface for extending server functionality.

type Hook interface {
	// When the client connects to the server
	// If the return is false, the client will be rejected.
	Connect(*Server, *Client) bool

	// When the client disconnects
	DisConnect(*Server, *Client, error)

	// When the server receives a packet.
	// If the return is false, it will cancel the operation.
	Recv(*Server, *Client, *packets.Packet) bool

	// When the server sends a packet.
	// If the return is false, it will cancel the operation.
	Send(*Server, *Client, *packets.Packet) bool

	// When the server receives a message from the client publish.
	// If the return is false, it will cancel the operation.
	Emit(*Server, *Client, *packets.Packet) bool

	// When the server pushes a message to the client
	// If the return is false, it will cancel the operation.
	Push(*Server, *Client, *packets.Packet) bool
}

With this interface, you can debug more easily, and:

func (*MyHook) Emit(server *mqtt.Server, client *mqtt.Client, pk *packets.Packet) bool {
    log.Printf("Client publish: %v, topic: %v, payload:%v", client.ID, pk.TopicName, pk.Payload)

    if pk.TopicName == "time" {
        server.PublishToClientByID(
            client.ID,  // client id
            "time_ack", // topic
            []byte(fmt.Sprintf(`{"time": "%s"}`, time.Now().Format(time.RFC3339))), // payload
            1,     // qos
            false, // retain
        )
    }

    return true
}

This code demonstrates that when a client sends a message with topic of "time" to the server, the server gives direct feedback to the client.

Contributions

Contributions and feedback are both welcomed and encouraged! Open an issue to report a bug, ask a question, or make a feature request.